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A  NEW  MANUAL 


or 


PHYSIOLOGY. 


A  COURSE  OF  LECTURES 


ON 


PHYSIOLOGY: 


DEUVBEED    BY    PROFESSOR    KJJSS    AT    THE    MEDICAL    SCHOOL    OP    THE 
UNIVERSITY    OF   STRASBOURG. 


Edited  by  MATHIAS   DUVAL,  M.D., 

Formerly  Demonstrator  of  Anatomy  at  the  Medical  School  of  Strasbourff ; 
Adjunctr-Proftssor  of  the  Medical  Faculty  of  Paris^  etc. 


^ranslatcti  from  tfje  ^ecottti  antr  Eetiseln  IStfitton 
By   ROBERT   AMORY,  M.D., 

FORMERLY    PROFESSOR    OF    PHYSIOLOGY    AT    THE    MEDICAL    SCHOOL    OF 
MAINE,    ETC. 


ILLUSTRATED  BY  ONE  HUNDRED  AND  FIFTY   WOODCUTS 
INSERTED   IN   THE    TEXT, 


-R 


•  BOSTOi^V 

1876. 


Entered  according  to  Act  of  Congress,  in  the  3'ear  1875,  by 

JAMES    CAMPBELL, 

In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


Press  of  JoJm  Wilson  6^  Son. 


K  9  6"cl 
/876 


PHEFACE 

TO  THE  AMERICAN  EDITION. 


DuKiNG  an  experience  as  a  teacher  in  the  department 
of  Physiology  at  the  Medical  School  of  Maine,  I  found 
it  a  difficult  matter  to  recommend  to  my  class  an  Eng- 
lish text-book  in  which  the  functions  of  living  tissue 
were  closely  compared  and  combined  with  its  texture, 
or,  in  other  words,  a  book  wherein  the  relations  of 
Physiology  to  Histology  were  carefully  presented.  Un- 
doubtedly there  are  many  good  works  on  Physiology  to 
which  the  student  can  refer  for  a  knowledge  of  the 
subject ;  but  a  concise  treatise  within  the  limits  of  the 
means  of  most  medical  students  cannot  be  found,  unless 
we  except  those  written  either  in  German  or  French. 
It  is  not  claimed  that  the  want  is  completely  met,  bat 
a  careful  study  of  this  manual  will  show  that  human 
Physiology  is  presented  in  a  concise  and  interesting 
manner,  and  that  recent  investigations  in  other  countries 
have  not  been  overlooked.  It  may  be  that  the  peculiar 
views  of  Professor  Kiiss  have  been  strongly  set  forth ; 
but  yet  it  must  be  remembered  that  the  positive  expo- 
sition of  a  teacher  in  any  department  of  instruction  is 
more  fruitful  to  the  cause  of  education  than  the  collec- 
tion of  a  vast  amount  of  undigested  material. 

"As  an  indication  of  the  general  method  of  the  author, 
we  would  direct  the  attention  of  the  student  to  the 
function  assigned  to  the  globule  or  cell  in  the  series  of 

13490 


VI  PREFACE. 

investigations  of  the  living  organism,  and  particularly  to 
the  office  of  the  epithelial  globules  in  absorption  and 
secretion.  The  time  is  come  for  science  no  longer  to 
explain  as  phenomena  of  osmosis  other  operations  of 
absorption,  secretion,  etc.,  which  belong  essentially  to 
living  bodies ;  but  to  attribute  these  and  similar  acts  to 
those  functions  or  offices  of  globular  or  cellular  ele- 
ments which  are  essentially  endowed  with  life,  espe- 
cially as  their  functions  cease  with  the  destruction  or 
death  of  these  elements. 

"  With  due  respect  for  those  positions  assumed  by  our 
author,  in  this  second  edition  we  have  avoided  giving 
too  great  prominence  to  any  theories  advanced  by  him 
which  seemed  to  bear  too  strongly  towards  the  hypo- 
thetical, and  reach  too  far  beyond  the  tangible  ground 
upon  which  the  science  of  to-day  rests ;  we  especially 
refer  to  the  study  of  the  functions  of  chyliferous  vessels 
as  connected  with  the  blood-vessels  in  the  process  of 
absorption." 

The  peculiarities  of  the  original  of  Professor  Kiiss  and 
the  French  editor.  Dr.  Duval,  have  been  conformed  to 
as  closely  as  consistent  with  the  French  idioms.  The 
method  of  the  author  is  concise  and  necessarily  techni- 
cal ;  and,  although  lucid,  demands  a  systematic  perusal 
of  the  work  for  its  comprehension.  An  explanation  of 
the  technical  terms  is  much  aided  by  diagrammatic  and 
other  forms  of  illustration ;  so  that  the  student  will  be 
rapidly  advanced  to  a  clear  view  of  the  whole,  as  to  the 
subject  and  terminology  employed. 

Though  an  efficient  compilation  may  be  thought  to 
serve  a  better  purpose  for  the  plan  of  a  general  text- 
book, no  objection  can  exist  against  special  works  by 
expert  physiologists  :  the  special  may  serve  as  an  intro- 
duction to  that  of  wider  extent. 


PREFACE.  vu 

Keeping  in  mind  that  our  primary  object  should  be 
to  afford  the  most  effective  aid  to  the  student,  the  body 
of  materials  has  been  enlarged  and  improved  upon  with 
judicious  additions,  new  illustrations,  and  biographical 
quotations.  We  have  endeavored  to  meet  the  want 
expressed  in  a  recent  review  of  a  distinguished  work  on 
Physiology,  that  of  "  a  well-digested  text-book  of  Phy- 
siology adapted  to  the  wants  of  the  advanced  studeat, 
nvhich  is  still  a  desideratum  in  American  scientific  \V:qv- 

ature If  the  foreign  books  upon  any  subject  are 

more  meritorious  than  those  of  our  own  country,  the 
preference  for  them  is  naturally  and  rightly  exercised. 
For  science  is  cosmopolitan ;  and  the  student  consults 
his  own  interests  and  that  of  science  at  large  by  supply- 
ing himself  with  the  most  useful  text-books,  no  matter 
Avhat  ma}^  be  their  nationality."  In  brief,  we  have 
made  every  effort,  within  the  limits  assigned  us  by  the 
original  plan,  to  lay  before  the  student  (and  the  physi- 
cian whose  time  will  not  allow  a  prolonged  study  of 
more  extensive  works)  a  satisfactory  treatise  on  Physi- 
ology in  its  present  stage. 

LONGWOOD,  January,  1875. 


CONTENTS. 


FIRST    PART. 
GENERAL  PHYSIOLOGY. 

I.  General  Physiology,  Cellular  Physiology 1 

Definition  of  Physiology.     Vital  phenomena,  2. 
Definition  of  life.     Cellular    physiology,  2.     Conservation 
of  force  and  of  matter,  3. 

IL   Concerning    the    Globule    or    Cell.  —  Its    Attributes 

AND  Historical  Review 3 

Size  of  the  globules,  3.  Their  shape,  4.  Color,  5.  Elas- 
ticity, 6.  Chemical  composition,  5.  Electro-motor  force, 
6.  Tenacity  of  composition,  7.  Life  of  the  globules,  7. 
Irritants  of  the  globules,  8.  Birth  of  the  globules,  9. 
Theory  of  the  blastema  of  Ch.  Robin,  9.  Segmentation, 
10.  'Functions  of  the  globules,  11.  Death  of  the  globules, 
12.  Excitants  and  excitability  (according  to  ancient 
physiologists,  Glisson,  Haller,  Tiedemann,  etc.),  13-15. 
Modern  notions  (Bichat,  Schwann),  16. 

IIL  The  Different  Kinds  of  Cells.  —  Their  Special  Prop- 
erties. —  Diagram  of  the  Organism.  —  Plan  op  this 
Manual  op  Physiology 16 

Segmentation  of  the  ovum  and  formation  of  the  blastoderm, 
17.  Layers  of  the  blastoderm,  17.  The  four  kinds  of 
globules :  epithelial,  18  ;  nerve,  blood,  and  embryonic,  20= 
Diagram  of  the  organism,  21.  Divisions  of  the  study  of 
Physiology,  22. 


SECOND    PART. 

THE  NERVOUS  SYSTEM. 

I.  A  General  View  of  the  Nervous  System 23 

Anatomical  elements  (cells,  nerve  tubes,  neurilemma,  etc.), 
25.  Researches  of  Ranvier,  26.  Life  of  the  nervous  sys- 
tem, 27.  Electro-motor  power,  28.  Action  of  the  ner- 
vous system :  reflex  action,  28  ;  centripetal  and  centrifugal, 
29.    Nerve  vibrations,  30.     Electrotonus,  31. 


X  CONTENTS, 

II.  General  Physiology  of  the  Nerve  Centres 31 

Nerve  centres,  gray  matter,  commissural  nerves,  spinal  cord, 
32.     Cerebral  substance,  33.     Cerebellum,  34. 

III.  Special  Physiology  of  the  Nervous  System    ....      35 

A.  Peripheral  nerves 35 

1.  Cranial  nerves:   Olfactory  and  optic,  35;  motores  oculorum, 

patheticus,  and  motor  oculi  externus,  36 ;  trifacial,  37 ; 
facial  and  auditory,  38 ;  glosso-pharyngeal  and  pneumo- 
gastric,  39 ;  hypoglossal  and  spinal  accessory,  40. 

2.  Spinal  nerves 40 

Anterior  and  posterior  roots,  and  recurrent  sensibility,  41. 
Ganglia  at  roots  of  spinal  nerves,  42. 

B.  Spinal  cord 42 

Paths  of  conduction,  43.  Neuroglia  of  the  spinal  cord,  44. 
Course  of  the  nerve  fibres ;  excitability  and  decussation 
of  fibres  in  the  cord,  45.  The  cord  as  a  nerve  centre,  46. 
Keflex  movements,  47.  Centres  of  deglutition,  mastica- 
tion, &c.,  49.  Classification  of  reflex  actions,  51.  Laws 
of  reflex  action,  52.  Variations  in  intensity  of  reflex  ac- 
tions, 54. 

C.  Encephalon 55 

Sensations,  general  and  localized,  66.  Associated  sensations, 
memory  and  volition,  57. 

Special  functions  of  certain  cerebral  centres,  69. 

Centre  of  faculty  of  language,  corpora  quadrigemina,  69. 
Cerebellum,  60.  Corpora  striata,  optic  thalami,  and  sen- 
sorium  commune,  61.  Corpus  callosum,  cerebral  hemi- 
spheres, 62. 

D.  Great  Sympathetic 63 

Bami  communicantes,  63 ;  ganglia,  64.     Vaso-motors,  66. 


THIRD    PART. 

CONTRACTILE  ELEMENTS,  MUSCLES  AND  THEIR 
APPENDAGES. 

I.  The  Muscles  in  General 67 

Origin  of  the  muscular  tissue,  cellular  fibre,  smooth  fibre, 
striated  fibre,  67.    Sarcous  elements,  68. 

II.  Striated  Muscles 68 

Under  form  No.  1,  69 :  elasticity,  70 ;  chemical,  72;  tonicity, 
electro-motor  force,  73.' 

Under  form  No.  2,  74  :  elasticity,  74 ;  chemical  phenomena, 
77 ;  mechanical  equivalent  of  heat,  78 ;  electro-motor 
force,  negative  variation,  80. 

Office  of  the  muscle  in  the  organism,  81 ;  its  irritability, 
etc.,  81.  Analysis  of  the  muscular  contraction,  84.  The- 
ory of  Rouget,  88. 


CONTENTS.  XI 

III.  Smooth  Muscles 92 

IV.  Contractile  Cells 94 

V.  Appendages  op  the  Muscular  System 94 

General  mechanism  of  the  muscles,  94.  Connective  tissue, 
95.  The  bones,  97.  Tendons  and  ligaments,  98.  Levers 
in  the  skeleton,  as  compared  with  the  three  kinds  of  levers, 
101.  The  articulations,  104.  Ligaments,  106.  Physiology 
of  the  movements  of  locomotion,  107. 


FOURTH    PART. 
BLOOD  AND  ITS   CIRCULATION. 

Concerning  the  blood,  110.  Quantity  of  blood  as  estimated 
by  Herbst,  Valentin,  Welcker,  111. 

Composition  of  blood,  112.  Cnior  and  white  globules,  113. 
Red  globules,  114.  Their  structure,  form,  and  size  in  man 
and  animals,  116.  Haemin,  117.  Hemoglobuline,  118. 
Absorption  spectra  of  blood,  119.  Function  of  the  red 
globules,  121.  Transformation  of  the  white  into  the  red 
globules,  123. 

Liquor  sanguinis,  125.  Fibrine  and  clot,  or  crassamentum, 
125.  Buffy  coat,  126.  Serum  of  the  blood,  127.  Fatty 
extractive  and  coloring  matters,  128.  Salts  and  gases  of 
the  blood  (Fernet),  129.  Albuminoid  substances,  Denis 
and  Schmidt,  130. 

Circulation  op  the  Blood 131 

Diagram  of  the  circulation,  131. 

I.  Central  Organ  op  the  Circulation 133 

Auricle,  133.    Ventricle,  valvular  system,  134.    Functions 

of  the  auriculo-ventricular  system,  135. 
Sounds  and  impulse  of  the  heart,  138. 
Table  of  movements  of  the  heart,  141. 

II.  Peripheral  Organs  op  the  Circulation 141 

A.  Mechanical  arrangement  of  these  organs. 

Vascular  cones,   141.    The  greater  and  lesser  circulation, 

142. 
Pressure  in  the  circulatory  system,  143.    Hemodynamometer, 

cardiometer,  144. 
Rapidity  of  circulation  of  blood,  laws  of  Poiseuille,  147 ; 

special  arrangements  of  the  circulation  in  certain  regions, 

150.    Portal  system,  150. 


Xil  CONTENTS. 

B.    Properties  and  functions  of  the  vessels. 

Arteries,  \b\.    Natural  form  of  the  arteries,  153.    Pulse,  155. 

Sphygmograph,   156.     Kymographion,   156.     Contraction 

of  the  arteries,  158. 
Capillaries,  159.     Inert  layer,  159.     Distinction  between  the 

different  kinds  of  capillaries,  160.     Their  structure,  161. 
Veins,  163.    Plexus,  163.     Valves,  164.     Vascular  sounds, 

164. 

III.  Influence  of  the  Nervous  System  on  the  Circulation     165 

Heart,  165.^  Moderating  nerves  of  the  heart,  166.  Acceler- 
ating nerves  of  the  heart,  167.  Cardiac  ganglia,  169. 
Vessels,  vaso-motor  nerves,  170.  Vascular  tonus,  172. 
Vascular  peristaltism,  173.  Vasomotor  centres,  176. 
Course  of  the  vaso-motor  nerves,  176.  Pathological  appli- 
cations, 178. 

IV.  General  Uses  of  the  Circulation 179 

Coagulation  of  blood  in  the  living  vessels,  181. 


FIFTH    PART. 

A  GENERAL  VIEW  OF  EPITHELIAL  GLOBULES  AND 
EPITHELIAL  SURFACES. 

I.  General  Anatomy  of  the  Epitheliums 185 

Serous  membranes,  185.  Integumentary  membranes,  186. 
External  and  internal  integuments,  186.  Ciliated  epithe- 
lium, 187. 

II.  General  Physiology  op  the  Epitheliums 190 

Their  function  in  presiding  over  the  phenomena  of  meta- 
morphoses of  the  tissues,  190.  Their  function  in  disease, 
191.  Lymphatic  system,  194.  Origin  of  the  lymphatics, 
195.  Composition  of  the  lymph,  197.  Perivascular  spaces, 
200.    Lymphatic  ganglia,  205.    The  spleen,  206. 


SIXTH    PART. 
DIGESTIVE   SYSTEM. 

I.  Object  of  Digestion,  Inanition,  and  Alimentation      .    .    209 

Proximate  principles,  or  elements  of  food,  210.  Hydrocarbons 
and  food  substitutes,  212.    Liebig's  extract  of  meat,  213. 

II.  First  Part  of  the  Act  of  Digestion 214 

Mastication,  214.  Insalivation,  216.  Ptyaline,217.  Salivary 
secretion,  218.  Deglutition,  223.  Concerning  the  reflex 
influences  of  deglutition,  229. 


CONTENTS.  xiii 

m.    SUB-DIAPHEAGMATIC   PORTION   OP   THE   DIGESTIVE   TrACK   .      231 

Formation  of  the  stomach,  small  and  large  intestine,  in  the 
foetus,  232. 

Stomach,  233.  Its  movements,  234.  Vomiting,  236.  Secre- 
tions in  the  stomach,  238.  Pepsin,  or  gasterase,  239. 
Gastric  j uice,  240.    Peptogeny,  242.     Chyme,  245. 

Small  intestines,  248.  Enteric  juice,  248.  Influence  of  the 
nervous  system  in  promoting  its  flow,  249.  Pancreatic 
juice,  249.  Pancreatogens,  251.  Movements  of  the  intes- 
tine, 253. 

IV.  Absorption 254 

Function  of  the  epitheliums,  and  diffusion,  254.  Intestinal 
villi,  and  their  oflace,  255.  Chyle  and  the  chyle-ducts,  256. 
Absorption  of  fats,  257.  Intestinal  desquamation,  bile, 
260.  Functions  of  the  liver,  265.  Kecent  researches  on 
the  biliary  capillaries,  267.  Glycogeny  and  diabetes,  268. 
Organs  of  absorption,  273. 

V.  Large  Intestine 276 

Its  movements ;  defecation,  277. 


SEVENTH  PART. 

PULMONARY  MUCOUS   SURFACE. —RESPIRATION. — 
ANIMAL  HEAT.  — PHONATION. 

I.   Respiration. 

I.  Anatomy  op  the  Respiratory  Surface 281 

Pulmonary  epithelium,  282.  Structure  of  the  respiratory 
membrane,  283.     Capillary  network,  its  extent,  286. 

II.  Mechanical  Phenomena  of  Respiration 287 

Inhalation,  288.  Mechanical  action  of  inhalation,  289.  Mus- 
cular action,  290.  The  use  of  the  diaphragm,  293.  Pas- 
sive action  of  the  lungs  accompanying  inlialation,  295. 

Expiration  or  Exhalation,  296.  Natural  form  of  the  lungs, 
297.    Forcible  or  active  exhalation,  299. 

Function  of  the  air-passages  in  respiration,  300.  Action  of  the 
trachea,  etc.,  during  respiration,  302.  Cougliing  and 
sneezing,  302. 

in.  Physical  and  Mechanical  Consequences  of  Respiration    803 

Mechanical  effects  produced  on  the  lung,  303.  Vital  capacity 
and  the  spirometer,  304.  Residual  air,  respiratory  air, 
&c.,  306.  Ventilation  of  the  lungs,  308.  Respiratory 
murmur,  &c,,  311. 

Mechanical  effects  produced  in  adjacent  regions  by  respira- 
tion, 312. 


XIV  CONTENTS, 

IV.  Chemical  Phenomena  op  Respiration 317 

Modifications  in  the  air  exhaled,  317.  Modifications  in  the 
blood  which  passes  through  the  lungs,  818.  Theory  of 
respiration,  321.  Respiration  of  the  tissues,  322.  OflSce  of 
the  blood  in  respiration,  323.  Function  of  the  pulmonary 
surface,  325.  Asphyxia,  328.  General  results  of  respira- 
tion, 331. 

V.  Influence  op  the  Nervous  System  on  Respiration    .    .    335 

The  respiratory  nerve  centre,  835.  The  centripetal  paths, 
836.     Centrifugal  paths,  338. 

II.  Animal  Heat. 

Source  of  the  animal  heat,  840.  Loss  of  heat,  842.  Influ- 
ence of  the  nervous  system,  345. 

III.   Larynx  and  Pronation. 

Structure  of  the  larynx,  glottis,  348.  Mechanism  of  phona- 
tion,  353.  True  vocal  cord,  355.  Appendages  to  the 
phonating  system,  trachea  and  pharynx,  etc.,  857.  Voice 
and  speech,  358.  Tone  and  pitch,  359.  Vowels  and  con- 
sonants, 360.    Innervation  of  the  laryngeal  system,  361. 


EIGHTH    PART. 
EXTERNAL  INTEGUMENT. 

I.  Structure  of  the  skin,  dermis 864 

Epidermis,  865.  Life  of  the  globular  elements  of  the  epider- 
mis, 866.  Epidermal  growths  (hair,  nails,  and  feathers), 
869. 

II.  Phenomena  of  exchanges  effected  by  the  skin 870 

Absorption,  370.  Secretions,  372.  Sweat  glands  and  per- 
spiration, 373.  Composition  of  sweat,  374.  Influence  of 
the  nervous  system,  376.  Uses  of  the  sweat,  877.  Seba- 
ceous secretion,  878.  Breasts  and  milk,  379.  Colostrum, 
880. 

IIL  Nerve  functions  of  the  skin 884 

Importance  of  cutaneous  sensibility,  884. 


NINTH    PART. 
ORGANS  OF  THE   SPECIAL  SENSES. 


General  Sensations 


Mucous  surfaces,  386.     Pulmonary  organs,  387.     Uro-genital 
mucous  membrane,  388.    Muscular  sense,  389. 


CONTENTS.  XV 

II.  Special  Sensations 891 

I.  Sense  of  Touch  and  Feeling 392 

Nervous  papillae,  393.  Tactile  corpuscles,  394.  Sensation 
of  varying  temperatures,  396.  Sensation  of  pressure, 
397.     Sense  of  localization,  398. 

II.  Sense  of  Taste 401 

Organs  and  seat  of  taste,  savors,  402.  Function  of  the  chorda 
tympani  (Lussana  and  Schiff),  406. 

III.  Sense  of  Smell 408 

Odorous  substances,  408.    Nasal  fossa,  olfactory  region,  410.    410 
Olfactory  nerves,  411. 

IV.  Sense  of  Hearing 412 

External  ear,  414.  Middle  ear,  416.  Mastoid  cells,  419. 
Eustachian  tube,  420.  Internal  ear,  421.  Analysis  of 
sounds,  422. 

V.  Sense  of  Sight 423 

1.  Dioptrical  apparatus  or  system,  424.    Media  of  the  eye, 

refraction,  426.  Accommodation,  428.  Emmetropia, 
myopia,  hypermetropia,  etc.,  431.  Mechanism  of  accommo- 
dation, 432.     Astigmatism,  434. 

2.  Membranes  or  envelopes  of  the  eye,  sclerotic  and  choroid 

coat,  435.     Iris,  438. 

3.  Sensitive  membrane  or  retina,  440.     Punctum  ccecum,  444. 

Yellow  spot,  445.  Office  of  the  rods  and  cones,  447. 
Radiation,  448.  Optical  illusions,  449.  Why  we  see  ob- 
jects erect  and  not  upsidedown,  450. 

4.  Appendages  of  the  eye,  muscles,  452.    Lachrymal  system, 

454.    Meibomian  glands,  456. 


TENTH    PART. 

URO-GENITAL  SYSTEM,  EMBRYOLOGY. 

Origin  of  the  uro-genital  system,  458.    WoMan  body,  459. 
Uro-genital  sinus,  459. 

I.  Urinary  System 460 

A.  Secretion  of  urine,  460.     Henle's  tubes,  461.     Glomeruli  of  the 

kidneys,  or  Malpighian  corpuscles,  461.  Renal  portal 
vein,  462.  Glomerular  filtration,  462.  Re-absorption  of 
albumen,  466.     Excretion  of  urea,  468. 

B.  Composition  of  urea,  468.     Anhydrous  urine,  469.    Extractive 

matters,  470.  Salts,  470.  Kiesteine,  471.  Influence  of 
the  nervous  system,  471. 

C.  Excretion  of  urine,  472.     Vesical    epithelium,   472.    How  the 

bladder  is  completely  emptied,  474.    Micturition,  476. 


XVI  CONTENTS. 

II.  Genital  System 477 

1.  Male  Generative  Organs 477 

Secretion  of  spermatic  fluid,  478.  Spermatozoids,  479. 
Erection,  482.  Erectile  systems  in  general,  484.  Ejacula- 
tion, 485.  Cowper's  and  Littre's  glands,  485.  Office  of 
the  prostate,  486. 

2.  Female  Generative  Organs 488 

Ovary  and  Graafian  vesicles,  488.  Ovulation,  489.  Yellow- 
body,  or  corpus  luteum,  492.  Menstruation,  493.  Vagina, 
494. 

III.  Fecundation  and  Development  of  the  Fecundated 

Egg 494 

1.  Fecundation,  494.  Caduca,  or  membrana,  497.  Development 
of  the  fecundated  egg,  499.  Envelopes  of  the  embryo 
first  chorion,  499 ;  umbilical  vesicle,  500 ;  amnion,  500 
second  chorion,  502;  allantois,  503;  third  chorion,  505. 
placenta,  506 ;  respiration  in  the  foetus,  507  ;  nutrition  of 
the  foetus,  507.  Development  of  the  body  of  the  embryo, 
608.  Nervous  system,  509.  The  circulations  in  the  em- 
bryo :  first  circulation,  510 ;  second  circulation,  512.  Sum- 
mary of  the  foetal  circulation,  518. 


COURSE  OF  LECTURES  ON  PHYSIOLOGY. 


PART   FIRST. 

GENERAL     PHYSIOLOGY. 

I.   Physiology.  —  Cellular  Physiology. 

THE  word  "physiology,"  or  "physiological  science,"  is 
difficult  to  define.  According  to  its  etymology  we 
should  interpret  it  as  the  science  of  growth  or  animation 
(cpvEiv).  The  word  "life"  or  "animation"  characterizes  the 
phenomena  which  exist  in  a  living  being.^  These  phenomena 
are  quite  complex,  and  the  history  of  science  presents  a 
crowd  of  definitions,  all  of  which  are  influenced  by  the  in- 
adequate state  of  the  knowledge  resulting  fi'om  observation 
at  diflferent  periods. 

If,  in  the  actual  state  of  our  anatomical  knowledge,  we 
examine  the  organic  elements  of  a  living  being,  we  find  that 
by  their  aspect  alone  we  can  divide  these  into  two  classes. 
One  class  is  thus  represented  by  the  purely  mechanical  (ves- 
sels, fibres)  or  chemical  office  (different  fluids)  which  these 
elements  must  render  to  the  organism.  Those  of  the  second 
class  appear  to  us  at  first  inexplicable  (globular  forms,  cells  ^), 
if  we  consider  their  functions  either  as  mechanical  or  chem- 
ical. 

If,  on  the  contrary,  we  examine  the  acts  of  which  the  living 
being  is  the  theatre,  we  meet  a  great  number  of  physical  and 

^  An  attempt  has  been  made  to  substitute  for  the  word  "  physi- 
ology "  that  of  "  biology,"  which,  by  its  etymology,  does  not  sig- 
nify science  of  life,  but  the  different  phases  of  life. 

'^  We  purposely  employ  the  words  "cell"  and  "globules" 
indifferently,  though  we  own  to  our  preference  for  the  word 
*'  globule." 


a  GENERAL  PHYSIOLOGY. 

chemical  phenomena  resembling  in  every  respect  those  pro- 
duced by  inanimate  nature :  thus,  the  eye  is  a  physical  and 
dioptric  apparatus ;  the  transformation  of  starch  into  sugar, 
in  the  mouth,  is  a  purely  chemical  fact.  But  we  meet, 
besides  these,  phenomena  which  can  be  explained  neither 
by  chemistry  nor  by  physics:  these  phenomena  deserve  a 
separate  study,  and  should  constitute  a  special  science  in 
a  department  whose  bounds  are  unlimited.  Such  phenom- 
ena are,  properly  speaking,  vital:  but  at  this  present  time 
we  can  only  give  a  purely  negative  definition  of  life ; 
viz.,  life  is  all  that  cannot  be  explained  by  chemistry  or  by 
physics. 

But,  whilst  all  the  chemical  and  physical  phenomena  are 
localized  in  those  portions  of  the  apparatus  that  are  simply 
mechanical  or  non-globular  (fibres,  vessels,  etc.) ;  whilst 
these  apparatus  present  to  us  always  the  same  essential 
aspect,  and  whilst,  for  example,  a  fibre  taken  all  by  itself 
can  often  offer  no  characteristic  features  by  which  we  can 
designate  it  as  young  or  old,  —  yet  the  phenomena  which 
are  neither  chemical  nor  physical,  in  other  words,  vital  phe- 
nomena, are  localized  in  the  globules  or  cells,  so  far  as  we 
can  now  by  the  process  of  elimination  suppose ;  this  is  also 
confirmed  by  observation ;  these  elements  are  presented  to 
our  view  as  continually  undergoing  changes ;  possessing  an 
ephemeral  existence  they  undergo  metamorphoses  of  form 
and  of  composition,  from  the  moment  which  we  can  call 
their  time  of  birth  to  that  which  constitutes  the  time  of 
death ;  in  short  they  are  endowed  with  age.  This  is  pre- 
cisely the  essence  of  those  phenomena  which  can  be  ex- 
plained neither  by  chemistry  nor  by  physics,  so  that  we  can 
say  life  is  the  correlation  of  successive  phenomena  presented 
by  the  globular  element,  and  can  define  in  a  positive  manner 
the  word  physiology,  as  the  study  of  the  globular  element  in 
its  metamorphoses.  Physiology  in  its  essence  can  to-day 
be  no  more  than  cellular. 

These  metamorphoses  are,  as  we  have  said,  "  changes  of 
form  and  composition."  Changes  of  composition  are  not 
necessary  to  characterize  life,  for  every  organic  body  in 
contact  with  the  air  will  absorb  oxygen  and  evolve  carbonic 
acid,  until  it  may  have  become  burnt  up  or  putrid.  The 
globule,  however,  far  from  being  destroyed  by  this  change,  is 
transformed,  i&  multiplied.  This  represents  its  life.  Cuvier 
defines  this  "  un  tourbillon  "  (vortex),  —  rather  an  incomplete 
definition,  because,  laying  aside  the  changes  of  form,  it  can 


OF  THE   GLOBULE  OR   CELL.  d 

be  applied  only  to  those  phenomena  of  changes  that  may  be 
likewise  encountered  in  dead  nature.^ 

These  metamorphoses  of  globular  elements  are  accom^ 
panied  by  chemical  and  physical  phenomena  that  cannot  be 
disregarded,  because  they  figure  as  effects  or  even  as  assist- 
ant causes  of  vital  acts ;  as,  for  example,  the  simple  mechan- 
ical transportations  (circulation)  whereby  the  globules  are 
brought  together.  Being  obliged  to  study  these  phe- 
nomena side  by  side  with  those  which  we  call  essentially 
vitjil,  we  can  say,  in  a  more  general  sense,  that  the  object 
of  ]»hysiol<)gy  is  the  study  of  all  the  phenomena  that  take 
place  in  the  organism.  Yet  it  is  with  the  cell  in  general 
that  we  should  commence  our  study,  and  around  this  we 
can  then  group  all  the  rest,  since  the  cell  alone  is  the  essen- 
tially vital  element.^ 


JI.   Of  the  Globule  or  Cell. — Its  Properties.  —  Histori- 
cal Review. 

Globules,  essentially  living  elements,  are  especially  char- 
acterized by  their  microscopic  dimensions ;  their  diameter 
varies  between  y^^  and  j§^  of  a  millimetre ;  one  only,  the 
ovum,  attains  a  size  sufficiently  large  to  be  distinguished  by 
the  naked  eye.  This  extreme  minuteness  explains  why  we 
could  not  recognize  what  might  be  called  the  essence  of 
vital  phenomena,  until  the  time  that  microscopes  gave  us  an 
opportunity  of  examining  the  extremely  small  objects  in 
which  these  vital  phenomena  have  their  seat. 

1  Vide  P.  Ad.  Housseau,  "  Role  et  Importance  du  Globule  en 
Physiologic."     These  de  Strasbourg,  1866,  No.  965. 

^  In  the  olden  time,  when  the  microscope  was  not  known  or 
used  in  the  study  of  living  tissues,  various  theories  of  vital  phe- 
nomena were  used  to  explain  the  principles  of  physiology.  At  one 
time  the  agency  of  spirits,  at  another  the  pneuma  or  breath,  at 
another  archaeus,  at  another  (^Xoyoy,  were  used  to  explain  the  occult 
causes  of  these  phenomena  ;  later  still  a  power  or  force  called 
vital  was  brought  forward.  An  insurmountable  objection  to  such 
theories  lay  in  the  fact  that  these  were  all  occult  agencies,  capable 
of  being  proved  simply  by  a  process  of  mental  reasoning,  and  re- 
sulting in  the  establishment  of  unsound  and  unavailable  doctrines. 
The  cell  theory  has  no  such  objection.  A  cell  can  be  seen  under  a 
microscope,  and  its  special  properties  studied  and  classified,  and 
the  doctrines  resulting  are  both  sound  and  available. 


GENERAL  PHYSIOLOGY. 


Should  we,  after  considering  their  minuteness,  consider, 
first,  their  physical  properties,  and  then  those  which  are  uni- 
versally vital  we  may  note :  — 

Their  Form.  —  All  the  globules  are  primarily  a  small  spher- 
ical mass,  homogeneous  and  compact.  This  form  they  pre- 
sent in  their  early  condition ;  but  afterwards  from  different 
causes  they  change  into  a  variety  of  forms  and  aspects. 
Thus  their  homogeneous  substance  can  be  divided  in  such  a 
way  that  on  the  inside  of  the  superficial  surface  solid  par- 
ticles may  be  grouped,  whilst  a  more  fluid  substance  will 
remain  about  the  centre,  and  a  kind  of  corpuscle  will  be 
formed,  having  a  limiting  membrane  with  its  contents.  Then 
the  globule  takes  the  form  which  merits  generally  the  name 
of  a  cell.     The  cell   reigns   almost  universally  throughout 

the   vegetable   kingdom;    in    the 

CvV /~\  /^^  animal  kingdom,  however,  without 
/#v\  //W^^  y^'^om  being  exclusive  we  prefer  gener- 
ally the  word  globule,  which  more- 
over recalls  the  primitive  and 
essential  form.  In  the  condition 
of  a  cell,  the  vital  element  is  com- 
posed of  an  amorphous  envelope, 
and  granular  and  transparent  con- 
tents, in  the  middle  of  which  a 
vesicle  is  seen,  called  a  "  germ  "  (nucleus),  which  itself  also 
encloses  another  germ,  called  a  nucleolus. 

Among  certain  physiologists,  all  these  parts  (envelopes, 
contents,  nucleus,  and  nucleolus)  must  be  present  in  order 
that  the  term  living  cell  should  be  legitimate ;  and  even  each 
one  of  these  parts  must  have  a  role  of  its  own,  the  contents 
presiding  over  the  function,  and  the  nucleus  over  the  repro- 
duction of  the  cell ;  this  is  perhaps  a  little  too  precise. 

Thus  many  observers  state  that  the  nucleus  disappears 
from  the  ovule  at  the  moment  the  latter  begins  to  become 
segmented,  that  is  to  say,  multiplied;  consequently  the 
word  "  cell "  is  not  so  general  that  we  could  adopt  it  to  the 
exclusion  of  the  word  "  globule,"  for  we  do  not  think  the  per- 
fect cell  is  met  in  every  place  where  the  phenomena  of  life 
are  observed,  and  that  these  latter  disappear  where  the  cell 
does  not  exist. 

Besides  this  grouping  in  the  primarily  homogeneous  mass, 
the  external  form  of  the  globules  can  undergo  an  infinite 
variety  of  form ;  as,  for  example,  by  the  process  of  nutrition 
the  globule  becomes  larger ;  again,  compressed  by  its  neigh- 


Fig.  i. 
Vegetable  cells  (from  the  potato). 


OF  THE  GLOBULE  OR   CELL.  5 

bors,  and  these  also  pressing  upon  each  other,  most  singular 
forms  are  assumed  in  which  we  ought  primarily  to  see  a 
sphere,  which,  in  fact,  may  often  be  found  in  the  deeper  or 
younger  layers.  Among  others,  as  for  instance  in  the 
globules,  the  relations  which  the  nerve  globules  must  form 
with  the  nej-ve  fibres,  oblige  the  former  to  divest  themselves 
of  their  typical  shape  to  throw  out  prolongations  in  stellate 
form.  Thus  and  from  other  causes,  as  will  hereafter  be 
observed,  we  find  in  the  worn-out  and  modified  globule 
polyhedral  forms  as  well  as  laminated,  cylindro-conical,  fusi- 
form, and  stellate  forms. 

Color.  —  Globules  generally  are  colorless,  though  certain 
have  divers  colors;  the  blood  globule  is  red.  Others  are 
pigment  globules,  that  is  enclosing  opaque  granulations, 
which  in  men  are  generally  dark  colored. 

Elasticity.  —  Globules  generally  are  endowed  with  con- 
siderable elasticity ;  thus  a  globule  flattened  by  some  phys- 
ical force  so  as  to  assume  a  discoid  shape,  may,  when  that 
force  is  removed,  retake  exactly  its  primary  shape.  This  is 
seen  when,  being  forced  to  traverse  through  a  narrow  orifice, 
the  globule  becomes  elongated  in  a  cylindrical  form,  and 
then,  after  emerging  from  the  pass,  again  assumes  its  round 
form. 

Chemical  Composition.  —  It  may  be  said  of  the  globules 
in  general,  that  their  chemical  composition  is  quite  com- 
plicated. The  dominant  element  is  water;  four-fifths  of 
the  weight  of  the  globule  is  made  up  of  this  element,  and 
this  forms  one  of  the  conditions  of  its  vitality,  for  water 
serves  as  the  menstruum  for  other  substances.  Thus  moist- 
ure may  be  considered  as  an  empirical  character  of  the 
life  of  a  globule;  cancers  which  are  only  an  excess  of 
globular  life  are  more  acute  when  they  have  a  more  moist 
consistency. 

Alter  the  water  in  line  of  importance  comes  albumen, 
this  substance  is  almost  characteristic  of  the  globule.^  The 
gluey  substance,  or  gelatine,  which  is,  on  the  contrary,  charac- 
teristic of  the  non-globular  elements  (connective  and  even 
elastic  fibres),  is  never  found  in  the  globules. 

In  addition  to  the  albumen  we  find  always  a  certain  pro- 
portion of  fat  bodies  in  a  state  of  intimate  combination  with 

^  This  is  what  gives  to  the  globular  masses  their  plasticity. 
Egg,  liver,  and  kidney  are  very  nutritious,  and  these  masses  are 
almost  entirely  composed  of  .globules. 


C  GENERAL  PHYSIOLOGY, 

the  preceding  elements,  especially  in  the  young  cells,  as  is 
proved  by  their  transparency ;  this  intimate  combination  of 
xjoater^  of  albumen^  and  of  fat^  is  apparently  one  of  the 
essential  dements  of  the  vitality  of  the  globide ;  when  the 
latter  attains  its  maturity,  the  fat  bodies  accumulate  in  it, 
and  then  only  are  they  seen,  apparently  in  a  free  state,  in 
the  form  of  spherical  beads,  giving  to  the  cell  an  opaque 
aspect.^  This  appearance  should  be  regarded  as  a  sign  of 
approaching  death  or  at  least  of  the  old  age  of  the  globule, 
which  will  either  soon  undergo  decomposition,  or  give  birth 
to  an  entire  generation  of  young  elements  in  which  the  fat 
will  be  concealed.  Consequently  an  abundance  of  water 
and  of  albumen,  which  is  characterized  by  great  transpar- 
ency, is  a  sign  of  life ;  excess  of  fat,  with  opacity  of  the 
globule,  is  a  sign  of  death.  When  a  tumor,  primarily  acute, 
begins  to  present  fatty  elements,  its  tendency  to  disappear 
may  be  predicted.^ 

Besides  these  three  principal  elements,  there  are  found 
others  in  small  quantities,  and  non-essential ;  these  are  the 
mineral  substances  which  make  up  the  general  composition 
of  the  body,  such  as  potassium  (in  state  of  potash  salts) 
and  phosphorus ;  these  two  substances  are  especially  found 
in  the  nerve  elements ;  also  sulphur,  incorporated  with  albu- 
men or  represented  by  its  salts.  The  same  may  be  said  of 
sodium,  calcium,  iron,  magnesium,  and  even  some  other 
metals.  It  answers  our  purpose  simply  to  note  the  fact  that 
the  globules  are  chemically  very  rich,  which  would  naturally 
lead  us  to  infer  what  part  these  bodies,  so  complex  in  com- 
position, would  perform  in  the  great  work  of  metamor- 
phoses. 

Electro-motor  Power.  —  Without  doubt  it  is  to  the  mul- 
tiplicity of  the  constituent  elements  that  the  globules  owe 
their  electro-motor  power;  this  property  of  disengaging 
electricity  is  especially  met  with  in  the  nerves  or  nerve  tubes 

*  Vide  J.  Straus,  •*  Essai  sur  la  Physiologie  de  la  Degdueres- 
cence  graisseuse  des  Muscles."  Th^se  de  Strasbourg,  1868,  No. 
124. 

2  So  when  fat  is  observed  m  those  elements  where  it  does  not 
belong,  serious  fears  for  the  future  should  be  apprehended.  M. 
Kiiss  has  observed  that  the  cancerous  tint  (a  characteristic  of  can- 
cerous cachexia)  is  to  be  looked  for  only  when  the  cancer  becomes 
fatty.  Thus,  by  the  aid  of  the  microscope,  he  could  tell  whether 
a  cancerous  mass  belonged  to  a  person  enjoying  every  appearance 
of  health. 


OF  THE  GLOBULE  OR  CELL.  7 

which  are  not  globules,  but  derive  their  properties  from  and 
are  in  intimate  association  with  these  globules. 

Tenacity  of  Composition.  —  But  of  all  the  properties 
belonging  to  their  composition,  the  most  important  and 
essentially  vital  is  their  tenacity  of  maintaining  their  consti- 
tution in  spite  of  the  surrounding  elements ;  and,  moreover, 
their  power  or  property  of  repelling  or  of  assimilating  cer- 
tain substances  by  a  veritable  selection.  Exposed  to  an 
atmosphere  greedy  of  moisture,  a  living  globule  does  not 
lose  its  watery  constitution ;  it  is  in  this  way  that  the  cells 
of  the  integument,  in  the  animal  as  in  the  plant,  maintain 
in  the  interior  of  the  organism  the  moisture  necessary  to 
life.  It  is  in  this  way  that  the  blood  globule,  rich  in  potash 
and  in  phosphates,  floats  in  a  fluid  (liquor  sanguinis)  rich 
only  in  soda  and  almost  destitute  of  the  preceding  salts,  and 
still  the  globule  retains  its  potash,  and  repels  the  soda  by  a 
veritable  phenomenon  of  repulsion,  essentially  vital.  Here 
the  laws  of  osmosis  lose  their  force,  for  they  encounter  living 
eletnents.  The  same  blood  globule  is  loaded  with  oxygen  in 
the  lungs,  and  becomes  the  vehicle  of  its  transport  through 
the  economy.  "We  can  also  cite  the  example  of  the  epithe- 
lium of  the  urinary  bladder,  which  offers  a  perfect  barrier  to 
the  passage  of  urine  through  its  walls,  a  passage  easily  effected 
six  or  seven  hours  after  the  death  of  the  patient,  and  then 
only  because  this  epithelium  has  ceased  in  its  turn  to  live. 

In  opposition  to  the  so-called  phenomena  of  rejection,  we 
have  another  instance  in  which  the  globule  favors,  on  the  con- 
trary, absorption :  thus  the  epithelium  of  the  intestine  at  a 
certain  time,  and  under  the  irritation  of  the  gastric  juice, 
allows  the  absorption  of  the  elaborated  aliments,  and  with  so 
much  rapidity  that  it  is  almost  impossible  to  study  the  details 
of  this  phenomenon. 

Life  of  the  Globule.  —  Its  life  is  in  our  eyes  the  most 
essential  characteristic  of  the  globule.  This  element  is  born, 
performs  its  functions,  and,  at  the  end  of  a  variable  time,  has 
a  tendency  to  disappear  by  means  of  very  various  transfor- 
mations. These  three  phenomena,  birth,  life,  and  death,  con- 
stituting the  metamorphoses  or  functions  of  the  globule,  occur 
only  under  the  influence  of  certain  excitants.^  In  the  vegeta- 

^  '*  Matter  in  itself  is  inert,  even  living  matter,  if  considered  in 
the  sense  of  deprivation  of  all  free-will.  Living  matter,  however, 
is  irritable,  and  can  itself  enter  into  activity  and  manifest  peculiar 
properties. ' '     (Bernard. ) 

We  shall  see  that  the  nerve  globule  itself,  which  in  the  first 


8  GENERAL  PHYSIOLOGY, 

ble  kingdom,  light,  heat,  and  doubtless  electricity,  constitute 
the  most  indispensable  excitants.  This  will  explain  why 
grains  of  corn,  found  in  the  tombs  of  the  pyramids,  have 
remained  dormant  during  long  periods  of  years  without 
showing  any  sign  of  life,  and  become  awakened,  or,  in  other 
words,  vegetate,  when  exposed  to  external  excitants.  The 
conditions  of  the  animal  globules  are  none  the  less  com- 
plicated; again,  a  certain  form  of  burning  produces  rapid 
changes  in  the  cells  of  human  skin,  in  the  epidermis.  These 
exciting  causes  may  be  physical,  chemical,  or  even  may  origi- 
nate in  the  interior  of  the  organism  (being  vital),  and  the 
principal  of  these  interior  (or  vital)  causes  is  most  certainly 
that  of  innervation,  or  the  influence  of  the  nervous  system 
upon  the  vital  elements.  Moreover,  the  actions  of  the  vari- 
ous excitants  may  succeed  each  other,  and  so  form  a  circuit 
of  influences,  alternating  in  character ;  in  this  way  the  ele- 
ments of  the  surfaces  (epithelium,  epidermis),  excited  by 
external  causes,  excite  in  their  turn  by  the  mediation  of  sen- 
sitive nerves  the  nerve  cells,  and  by  means  of  the  motor- 
nerves,  convey  the  excitation  to  the  muscles  or  to  other 
elements  on  the  surfaces,  as,  for  instance,  the  glandular  epi- 
thelium, and  consequently  we  may  have  vital  excitations  pro- 
duced by  excitations  which  were  at  first  only  mechanical. 

Let  us  note,  moreover,  that,  with  certain  globules,  these 
excitations  may  cause  a  special  action :  thus,  the  gastric  juice 
irritates  the  intestinal  epithelium,  and  no  other ;  again,  the 
spermatic  corpuscle  is  the  sole  excitant  of  the  ovule,  and 
thus  efficiently  arouses  its  functional  activity  or  its  develop- 
ment. 

Briefly,  these  excitants  can  act  with  varying  degrees  of 
intensity.  In  the  highest  degree  these  may  immediately 
destroy  the  globule ;  thus  poisons  act  more  especially  upon 
one  or  another  group  of  globules,  and  thus  cause  their 
destruction. 

It  is  difficult  to  explain  the  nature  of  the  phenomena  by 
which  an  excitant  acts  on  a  cell.  Sometimes  this  has  been 
compared  with  the  so-called  catalytic  action,  whose  especial 
characteristic  consists  of  the  flict,  that  the  body  neither  gives 
nor  takes  any  thing  from  the  excited  body  (phenomena  of 

place  seems  to  enjoy  free-will,  can  only  transmit  or  reflect  irrita- 
tions that  are  received  from  different  sources.  Those  acts  which 
seem  on  superficial  examination  the  result  of  nerve-spontaneity, 
are  really  only  reflex  actions. 


OF  THE   GLOBULE  OR   CELL,  9 

contact).  But  it  is  not  so  with  the  living  globule  ;  the  phe- 
nomenon is  more  complicated  ;  thus  oxygen  excites  the  blood 
globule  and  modifies  its  form  because  it  penetrates  the  glob- 
ule. The  epithelium  of  the  intestine,  excited  by  the  gastric 
juice,  imdergoes  a  change,  but  if  this  continues  too  long,  it 
becomes  more  opaque,  etc.,  showing  that  it  has  received  an 
addition  of  substance. 

Let  us  now  turn  our  attention  to  those  phenomena  pre- 
sented by  the  globules  when  under  the  influence  of  physical, 
chemical,  and  vital  excitants. 

Birth  of  the  Globules.  —  No  one  has  really  observed  the 
formation  of  cells  in  the  midst  of  an  amorphous  liquid 
(blastema).^ 

*  The  theory  of  voluntary  formation  of  cells  in  a  fluid  more  or 
less  amorphous  dates  as  far  back  as  the  time  of  Schleiden  and 
Schwann,  1838,  and  even  now  by  C.  Robin.  Schwann  called  the 
liquid  in  which  the  generation  was  supposed  to  take  place  cytohlas- 
tema.  Raspail  compared  the  formation  of  the  cell  in  this  cytoblas- 
tema  to  that  of  crystals  in  a  liquid  which  held  in  solution  the  crys- 
talline substance.  Schwann  had,  however,  observed  and  described 
the  facts  of  segmentation,  but  considered  these  accidental  and  in 
no  wise  general.  To-day,  and  especially  since  the  works  of  Remak 
upon  the  formation  of  the  blood  globules  (by  segmentation) ,  it  is 
generally  admitted,  in  accordance  with  the  doctrine  of  Virchow, 
that  every  cell  comes  from  some  pre-existing  cell  (omnis  cellula  a 
cellula  et  in  cellula).  However,  the  theory  of  the  Blastema  or 
genesis  is  still  defended  in  France  by  eminent  histologists,  by  a 
numerous  school,  and  especially  by  Charles  Robin.  Robin's  theory 
of  genesis,  moreover,  differs  in  many  points  from  the  ancient 
theory  of  Schwann.  Thus,  the  media  in  which  the  genesis  occurs, 
the  blastemata  (blood,  lymph,  interstitial  fluids)  are  themselves 
the  products  of  pre-existing  cells  in  such  fashion  that  the  newly 
formed  elements  have  come  from  older  cells,  not  indeed  directly, 
but  by  mediation  (substitution)  of  a  hquid.  The  manner  of  the 
production  of  the  theoretical  genesis  consists  in  the  spontaneous 
appearance  of  a  nucleus  which  is  surrounded  by  the  thickened 
blastema ;  or  else  the  mass  of  the  blastema  is  divided  into  globular 
islets,  each  of  whose  centre  has  a  newly  formed  nucleus.  Accord- 
ing to  this  the  nucleolus,  which  may  be  afterwards  formed,  is  a 
secondary  element,  whilst  Schwann  considers  the  nucleolus  as  the 
point  of  departure  of  cellular  formations.  In  brief,  formation  by 
genesis  occurs  under  conditions  and  periods  that  may  be  stated  in 
a  general  way,  as  follows :  1st,  By  the  formation  of  male  or  female 
ovula  (spermatozoidal  cells);  2d,  by  the  formation  of  the  embry- 
onic tissues  by  layers  of  blastoderm;  3d,  in  the  full-grown  animal 
by  the  production  and  renewal  of  the  epitheliums  and  epiderm ; 
4th,  and  finally,  it  is  to  this  manner  of  formation  that  almost  alli 


10 


GENERAL  PHYSIOLOGY. 


The  study  of  the  growth  and  reproduction  of  those  epi- 
theliums formed  only  from  cells,  especially  the  numerous 
pathological  products,  tends  to  prove  that  every  globule  is 
born  of  another  globule  {omne  vivum 
ex  ovo).  In  this  point  of  view,  the 
question  of  spontaneous  generation  is 
gradually  losing  confirmation  by  obser- 
vation. Considering  then  that  every 
globule  springs  from  another  globule,  the 
type  in  accordance  with  which  this  gen- 
eration takes  place  is  represented  by  the 
ovum.  At  a  certain  stage,  when  all  the 
suiTounding  circumstances  are  favorable, 
the  mother-cell  presents  the  appearance 
of  a  supei^ficial  strangulation,  which  grad- 
ually grows  more  prominent,  and  finally 
divides  the  primitive  globule  into  two 
globules.  As  soon  as  the  first  division  has 
been  accomplished,  another  strangulation 
occurs  at  right  angles  to  the  first ;  —  thus 
finally  subdividing  each  globule,  so  that, 
in  the  place  of  our  original  globule,  we 
have  four  globules.  We  shall  have  occa- 
sion for  the  detailed  study  of  these  phe- 
nomena, when  we  consider  the  formation 
of  the  diflerent  globules,  in  particular  the 
ovule,  under  the  head  of  segmentation 
of  the  vitellus.  Sulfice  it  now  to  mention 
that  in  a  general  way  every  cell  is  born 
Fig.  2.— Various  sncces-  of  another  cell  by  the  process  called  seg- 

sive  degrees  of  Inter-  ...  jt.         lu*  .^x- 

section  and  segmenta-  mentation,  and  when  this  segmentation 
tion  of  a  globule  (ovum   concerns  onlv  the  portion  contained  within 

from  frog,  Baer).  J  .      ,  ^r 

the  envelope,  it  is  called  Anaogenests,  or 
when  both  envelope  and  contents  are  involved,  forming  thus 


the  pathological  neoplasms  owe  their  origin.     In  all  other  cases  the 
cellular  theory  asserts  its  rights. 

In  a  recent  work,  Onimus  published  a  number  of  experiments 
which  seem  to  prove  that  the  globular  elements  .(white  globules  of 
blood  and  of  lymph)  can  be  formed  in  the  serous  fluids,  in  lymph 
maintained  under  proper  conditions  of  temperature,  of  surround- 
ing media,  and  of  molecular  changes.  This  work  has  met  with 
considerable  opposition,  and  it  is  not  right  to  pronounce  now  upon 
this  point.  We  may  draw  our  conclusions  in  the  following  words 
of  Frey:  "  Though  every  thing  seems  to  prove  that  the  animal 


OF  THE   GLOBULE   OR   CELL.  11 

a  homogeneous  mass  (which  is  correctly  speaking  a  globule)  ; 
this  constitutes  fissiparons  propagation  (one  variety  only  of 
which  is  the  budding).  The  latter  method  is  the  most  fre- 
quent means  of  proliferation ;  thus  all  globules  resemble  each 
other,  not  only  with  respect  to  their  mode  of  origin,  but  even 
as  to  their  primitive  globular  form. 

Function  of  the  Globules,  —  When  once  formed,  globules 
under  the  influence  of  certain  excitants  perform  their  func- 
tions in  different  ways.  One  kind  are  simply  endowed  with 
the  property  of  changing  their  shape  ;  as,  for  instance,  certain 
globules  of  the  skin  of  the  batrachians,  under  the  influence 
only  of  light  as  an  excitant,  change  from  a  spherical  into  a 
stellate  and  even  a  fibrous  form.^  This  change  of  form  is  what 
was  for  a  long  time  recognized  under  the  name  of  contrac- 
tion. So  the  blood  globules,  when  exposed  to  oxygen,  become 
more  flat  than  before,  a  phenomenon  which  can  also  be  effected 
by  the  presence  of  sodium  chloride,  and  certain  other  neutral 
salts ;  and  this  would  seem  to  prove  that  the  change  is  due 
to  a  chemical  phenomenon.  We  could  also  cite  as  examples 
of  change  of  form  or  of  contraction  the  movements  of  the 
vibratile  cilia,  with  which  the  free  surface  of  certain  of  the  epi- 
thelial cells  are  provided,  which  movements  certainly  are  con- 
nected with  cell  life  and  in  no  wise  dependent  upon  the 
medium  of  the  nervous  system,  since  forty-eight  hours  after 
death  they  can  be  made  to  reappear  under  the  influence  of 
a  dilute  solution  of  potassa  or  soda. 

Finally,  all  that  has  been  said  of  the  cells  under  the  head 
of  composition,  tenacity  of  self-maintenance,  the  attraction 
they  exercise  on  certain  chemical  substances,  their  electro- 
motor power,  etc.,  constitute  their  life.  Farther  on  these 
elements  of  vitality  will  be  considered  separately  for  each 
globule.  It  should,  however,  be  here  remarked  that,  wher- 
ever in  the  organism  vital  manifestations  are  observed,  these 
are  found  localized  in  special  cells ;  for  instance,  certain  cells 
in  the  liver  secrete  bile,  others  sugar,  or  a  glycogenic  sub- 
stance ;  again  sensibility  is  localized  in  the  nerve  cell,  etc. 

cells  cannot  be  formed  spontaneously,  it  is  not  without  interest, 
nor,  perhaps,  without  advantage,  to  find  defenders  for  the  ancient 
theories  and  enemies  to  the  new  (cellular)  doctrine.  Science  will 
be  thus  placed  in  a  position  to  furnish  to  the  facts  every  support 
which  belongs  to  them,  and  the  study  of  the  tissues  can  but  gain 
thereby." 

^  These  changes  of  form  involve  changes  of  color,  even  in 
globules  containing  no  pigiuent. 


12  GENERAL  PHYSIOLOGY. 

Death  of  the  Globules.  —  The  globule  being  essentially 
ephemeral,  at  a  certain  stage  after  the  special  manifestations 
of  some  of  the  above-named  phenomena,  it  becomes  trans- 
formed and  disappears.  However,  some  of  them  may  con- 
tinue in  the  cell  condition  for  many  years,  but  they  no  longer 
live  ;  they  pass  into  a  dormant  state,  which  can  even  be  com- 
pared with  their  death.  This  fact  is  very  common  in  vege- 
table life ;  it  is  rather  uncommon  to  see  in  man  cells  whose 
fiinctions  have  ceased,  or  which  have  lost  their  characteristic 
vitality,  though  still  preserving  their  cellular  formation.  We 
can  cite,  however,  certain  pigment-cells,  those  of  the  uvea 
(pigment  at  the  posterior  surface  of  the  choroid  and  iris) 
which  no  longer  manifest  the  physical  properties  of  their 
pigment,  but  by  the  absorption  of  the  luminous  rays  of  light 
preserve  thereby  the  functions  of  the  eye  intact.  We  could 
also  cite  in  this  connection  those  globules  to  be  hereafter 
studied  under  the  name  of  embryonic  or  plasmatic  cells. 
These  seem  to  lie  dormant  in  the  midst  of  connective  tissue ; 
but  when  submitted  to  an  exciting  influence  suddenly  awake, 
and  spring  into  action,  either  in  the  restoration  of  breaches 
made  in  the  tissue,  or  in  giving  origin  to  new  products,  gen- 
erally of  a  pathological  character.  But  the  real  death  of 
the  globules,  the  final  loss  of  their  individuality,  may  happen 
iu  two  ways. 

In  the  first  case,  the  globule  has  little  or  no  specified  form. 
It  may,  indeed,  dry  up  and  fall  into  a  state  of  fine  dust  (fur- 
furaceous  deposits,  and  continued  desquamation  of  the  sur- 
face of  the  epiderm) ;  these  scales,  and  pulverulent  remains 
that  constitute  the  epidermal  scales,  can  be  made  to  resume 
their  cellular  shape  by  being  placed  in  an  alkaline  solution  ; 
still  this  is  simply  the  corpse  of  the  globule,  a  simple  physical 
imbibition,  and  the  regenerated  globular  form  is  only  a  form ; 
there  is  no  longer  life.  Yet,  most  frequently,  the  globule  be- 
comes infiltrated  with  fat,  or  other  matters  upon  which  it 
may  exert  a  powerful  attraction ;  in  this  case  it  becomes 
liquid,  and  falls  in  the  form  of  deliquium,  and  thus  may  result 
various  kinds  of  fluids.  This  is  the  mechanism  of  most  of 
the  secretions,  and  so  also  of  most  of  the  fluids  secreted. 

In  the  second  case,  the  globules  lose  their  globular  shape, 
but  give  birth  to  many  new  anatomical  forms,  in  soldering  or 
fusing  one  kind  with  another;  as,  for  instance,  to  form  fibres, 
or  canals.  This  is  the  origin  of  the  non-cellular  portions  of 
the  organism ;  fibres  formed  in  this  way  can  no  longer  exhibit 
the  vital  properties  of  those  globules  from  which  they  were 


OF  THE   GLOBULE  OR   CELL.  13 

begotten,  but  only  possess  characteristics  distinctly  physical, 
such  as  elasticity,  toughness,  etc.  However,  there  are  some, 
forming  a  separate  class,  which  possess  even  in  a  higher 
degree  the  properties  characterized  by  the  primitive  globule, 
as,  for  instance,  the  muscular  fibre,  which,  in  addition  to 
its  elasticity,  is  endowed  with  an  electro-motor  as  w^ell  as 
even  a  still  more  essential  property,  that  of  changing  its 
form  under  the  influence  of  excitants.  The  nerve  fibre  pos- 
sesses properties  not  exactly  similar  to  the  above,  but  yet 
highly  characteristic  of  the  condition  of  life. 

These  are  the  principal  phenomena  presented  by  the  gen~ 
eral  review  of  cellular  physiology.  As  before  remarked,  they 
all  occur  under  the  influence  of  excitants  or  irritants.  We 
have  shown  how  these  may  be  divided  into  physical,  chemi- 
cal, or  vital,  this  division  being  sufliciently  accurate  for  the 
physiologist,  though  the  most  diverse  excitants  may  cause  the 
same  efi*ect;  for  example,  a  shock  or  simple  touch  brings 
about  cellular  contraction,  especially  in  the  muscles;  elec- 
tricity, or  certain  acids  even,  produce  the  same  phenomenon, 
which  is  naturally,  in  the  physiological  condition,  almost  ex- 
clusively manifested  under  the  influence  of  the  nervous  sys- 
tem. A  more  interesting  division  would  be  based  upon  the 
nature,  not  the  effects  of  the  excitant.  This,  unfortunately,  is 
impossible.  Yet,  following  out  this  plan,  some  have  tried  to 
recognize  three  kinds  of  irritability :  irritability  of  formation 
or  of  development,  trophic  or  nutrient  irritability,  and  func- 
tional irritability.  We  have,  however,  seen  how  the  different 
phenomena  of  development,  nutrition,  function,  and  even 
death,  form  a  physiological  product  that  should  artificially  be 
subdivided  for  convenience  of  study. 

Can  the  irritability  of  development  be  separated  from  that 
of  nutrition.  Have  we  not  also  seen  that  cells,  those  of  the 
glands,  for  instance,  perform  their  chief  function  by  disap- 
pearing as  a  cell  element,  and  then  becoming  liquefied,  appear 
as  a  secretion?  An  attempt  has  been  made  to  divide  the 
functions  of  the  isolated  globule  as  well  as  those  of  the  entire 
organism  into  three  great  classes,  viz. :  relation,  reproduc- 
tion, and  nutrition,  as  if  the  functions  of  reproduction  were 
not  concerned  in  either  of  the  two  other  divisions. 

The  theory  that  life  resides  in  the  excitable  elements  re- 
acting differently  with  different  excitations,  is  quite  ancient, 
and  the  history  of  the  words  excitant^  excitability,  and  of 
those  synonymes  which  have  turn  by  turn  taken  their  place, 
as,  for  instance,  irritant^  irritability^  incitant^  incitability^ 


14  GENERAL  PHYSIOLOGY. 

etc.,  make  up  the  true  condition  of  physiology,  as  well  as  of 
the  science  of  life,  or  science  of  living  matter.  An  era  of 
complete  darkness,  that  is,  of  pure  hypotheses,  followed  the 
time  of  Galen,  who  had  with  difficulty  enounced  this  theory.^ 
Neither  Descartes,  Newton,  nor  Boerhaave  had  any  thing  to 
do  with  physiology ;  they  simply  applied  the  facts  of  mecha- 
nism and  physics  to  living  beings. 

Glisson  (in  l^l'l)  was  the  first  to  suggest  the  word  "  irri- 
tability," which  he  considered  a  characteristic  property  of 
living  beings ;  a  property  determining  the  organic  move- 
ments, and  which  is  set  in  motion  by  causes  either  from 
without  or  from  within,  which  he  calls  irritant  causes.  But 
these  theories  by  which  Glisson  characterized  life  in  a  manner 
so  remarkable  for  his  time,  passed  unnoticed  by  his  contempo- 
raries; and  we  see  with  Stahl  (1708),  and  then  with  Barthcz, 
the  teaching  of  the  animists  and  the  vitalists  coincide  alrliost 
exactly  with  the  ancient  theories  of  a  fundamental  force 
(V^^ri)»  upon  which  depend  all  the  manifestations  of  life.^ 

^  The  ancients,  among  them  Hippocrates,  Plato,  and  Aristotle, 
being  almost  entirely  without  observations  or  experiments,  were 
busied  with  the  essence  of  life^  founded  on  pure  hypothesis,  char- 
acterized generally  by  their  belief  in  a  principle  of  fife  distiuct 
from  matter  {^vxh  of  Aristotle),  hypotheses  which  were  soon  to 
reappear  under  the  name  of  animism  and  vitalism.  Galen,  turn- 
ing his  attention  to  anatomy,  rejected  the  purely  speculative  doc- 
trines, but  still  his  physiology  was  only  a  logical  inference  from 
anatomy,  for,  wisely  keeping  within  certain  bounds  furnished  by 
his  observation,  he  sought  only  the  part  played  by  the  different 
organs  (jie  usupartium).  This  should  be  the  true  spirit  to  preside 
over  the  study  of  physiology.  Under  such  an  idea  Galen  deserves 
indeed  the  title  of  "  The  Father  of  Physiology."  The  physiolo- 
gists of  the  present  time  add  only  what  has  been  obtained  by  means 
of  investigation,  and  consequently  obtain  results  far  different.  Being 
able  to  study  the  organs  only  macro-graphically,  Galen  was  obliged 
to  look  upon  their  functions  simply  as  nearljr  mechanical;  now  the 
microscope  reveals  to  us  the  globule,  which,  in  the  order  of  things, 
we  can  consider  as  the  strictly  vital  element.  Studying  the  prop- 
erties and  functions  of  these  cells  in  the  same  way  that  Galen 
studied  those  of  the  organs,  we  may  perhaps  attain  the  true  knowl- 
edge of  vital  phenomena,  without  having  recourse  to  hyjjotheses: 
life  will  be  really  represented  by  the  cell  reacting  under  the  influ- 
ence of  excitants.  An  organ,  even  the  whole  organism,  will  be  a 
union  of  cells,  as  an  association  is  a  union  of  individuals.  {Vide 
CI.  Bernard,  "  Legons  sur  les  Propriet6s  des  Tissus  Vivants." 
18G6.) 

2  Stahl  would  not  admit  that  living  matter  had  vital  activity  or 


OF  THE   GLOBULE  OR  CELL.  15 

With  Haller  reappears  Glisson's  expression,  "  irritability." 
Though  but  theoretically  showing  that  irritability  was  a 
property  of  living  matter,  Haller  experimented  directly 
upon  living  animals;  his  vivisections  gave  him  an  oppor- 
tunity especially  of  studying  muscles,  and  he  applied  the 
word  "  irritability  "  particularly  to  the  muscular  system  ;  if 
he  went  no  farther,  still  he  used  the  experimental  method 
of  study,  and  the  theory  of  irritability  took  its  definite  posi- 
tion in  science.  Brown  (1780)  generalized  this  term  under 
the  special  names  of  "  incitability '  and  of  "  incitants  "  (mcitOr- 
menta)^  giving  a  name  to  that  property  possessed  by  living 
matter,  of  performing  its  functions  under  the  influence  of 
external  causes,  without  the  intervention  of  any .  distinct 
principle  of  the  organism.^  Tiedemann  carried  out  the  same 
principle  by  substituting  for  the  words  "  incitants,"  "  incita^ 
bility,"  those  of  "  excitability,"  and  "  excitants."  But  yet,  if 
the  words  "  excitability,"  "incitability,"  or  "imtability,"  in 
spite  of  their  variety,  express  area!  property,  the  value  and 
limitation  of  the  words  "  living  matter,"  to  which  these 
authors  attribute  the  property,  is  not  precisely  defined. 
Moreover,  they  do  not  agree  in  regard  to  its  definition. 
Haller  seems  to  consider  that  the  muscle  almost  alone  is 
irritable,  whilst  Brown  considers  all  the  solid  portions  of  the 
organism  are  incitable;  but  not  so  with  the  liquids.  And 
again,  Tiedemann  would  allow  excitability  to  both  liquids 
and  solids.  This  confusion  existed  even  to  the  time  when 
general  anatomy  was  founded  upon  histology,  as  revealed  by 
the  microscope.  Now  the  cell  must  be  recognized  as  the  primi- 
tive element  of  the  organism.  We  have  seen  that  it  alone 
is  the  seat  of  vital  phenomena,  that  it  alone  is  excitable  in 
8ome  tissues ;  as,  for  instance,  the  muscles,  which,  being  de- 
irritability,  and  supposed  a  vital  force,  independent  of  organic 
elements,  an  immaterial  substance,  the  soul  (not  to  be  confounded, 
however,  with  the  soul  of  philosophers  and  theologians,  which  is 
not  the  same  as  that  which  is  called  ' '  soul  "  by  physiologists) ,  which 
is  endowed  with  absolute  free-will,  and  presides  alone  over  the 
functional  movements  of  our  organs.  Such  is  the  animism  of 
Stahl,  which  later  reappears  in  several  schools  imder  the  name  of 
vitalism.  The  vitalists  substitute  simply  for  the  word  "soul" 
"vital  force,"  or  "vital  principle,"  a  hidden  quality,  a  funda- 
mental force  whence  spring  all  the  manifestations  of  life. 

*  The  whole  medicine  of  Broussais  is  but  a  theory  of  incitants 
imported  from  physiology,  and  applied  to  pathology.  These  are 
pathological  incitants,  and  all  diseases  come  from  irritations.  For 
details  vide  CI.  Bernard,  "  I'ropriete  des  Tissus  Vivants." 


16  GENERAL  PHYSIOLOGY, 

rived  from  cells,  have  preserved  these  properties.  The  irrita- 
bility of  Glisson  and  Haller,  the  incitability  of  Brown,  the 
excitability  of  Tiedemann,  are  precisely  the  characteristic 
property  of  the  cell,  and  in  this  point  of  view  the  exact 
expression  that  the  essence  of  vital  phenomena  represents 
to  us. 

It  is  due  then  to  the  powerful  means  of  study  furnished  by 
the  microscope  that  we  owe  the  idea  that  we  are  formed 
from  vital  phenomena ;  but  it  would  be  unjust  not  to  men- 
tion in  this  connection  the  name  of  Bichat,  who,  by  his  en- 
dear ors  in  the  study  of  general  anatomy^  pointed  out  the 
fact  that  the  foundation  of  the  science  of  histology  should 
be  established  by  means  of  micro-graphy.  The  introduction 
of  the  microscope  in  the  seventeenth  century  in  the  hands 
of  Malpighi  and  Leeuwenhoek  resulted  more  in  obsei*va- 
tions  of  simple  curiosity  than  in  scientific  researches,  at  least 
for  the  study  of  animal  tissues.  At  the  commencement  of 
this  century,  Bichat  founded  general  anatomy,  and  aimed  at 
the  study  and  classification  of  the  human  tissues ;  but  making 
use  only  of  dissections  by  the  unaided  eye,  of  chemical  re- 
actions, and  of  physiological  and  pathological  investigations, 
he  could  grasp  but  a  few  of  the  gross  characteristics  that 
distinguish  the  tissues.  But  as  soon  as  the  path  had  been 
pointed  out,  and  the  microscope  was  established  for  the  re- 
search of  organic  elements,  Schwann  was  enabled  in  1839  to 
attempt  the  study  of  the  tissues,  by  starting  with  the  cell 
and  founding  histology,  or  what  might  be  called  general 
anatomy  studied  by  means  of  the  microscope.  Physiology 
and  Pathology  were  the  necessary  consequence. 


in.  — Different  Kinds  of  Cells.  —  Their  Particular  Func- 
tions. —  Diagram  of  the  Organism.  —  Plan  of  Study  of 
Physiology  in  this  Treatise. 

At  its  origin  an  organism  is  formed  of  a  single  cell,  tho 
ovum,  which  has  already  been  mentioned,  and  whose  segmen- 
tation has  also  rapidly  been  described,  as  a  type  of  gener- 
ation or  of  proliferation  of  the  class  of  globules  in  general. 
From  the  segmentation  of  the  vitellus,  or  contents  (proto- 
plasm) of  the  ovum,  the  envelopirg  membrane,  or  zona  peU 
lucida,  is  formed,  enclosing  a  large  number  of  globules 
resembling  each  other ;  but  after  a  while  these  globules  begin 
to  vary  in  their  foi*m  and  position. 


DIFFERENT  KINDS  OF  CELLS,  17 

At  first,  these  globules  are  grouped  towards  the  periphery 
of  the  cavity  of  the  primitive  (Fig.  3)  ovum,  and,  in  this 
way,  form  a  membrane  which  we  shall  study  under  the  name 
of  epithelium.  As  in  the  perfected  organism,  an  epithelium 
rests  upon  a  fibrous  or  undetermined  tissue,  so  also  does  the 
ovular  epithelium  rest  upon  the 
membrana  pellucida  (Fig.  3,  A). 
We  see  then  even  at  this  stage 
(and  great  importance  must  be 
attached  to  these  forms)  the  organ- 
ism represented  successively  by  a 
cell,  and  secondly  by  an  epithelium ; 
this  latter  might  be  called  epithe- 
lium of  thezona pellucida  (Fig.  3  B) ; 
and  as  this  serves  as  the  germ  of  ^,  ^^'  ?;,   ^  ^ 

n    .1  ^1  j_'  '.L   1,        1  Diagram  of  the  Blastoderm.* 

all  the  other  portions  it  has  been 

called  the  germ-m,embrane,  or,  more  generally,  blastodermic 

membrane,  or  blastoderm. 

This  change  of  position  of  the  globules,  whence  a  globular 
membrane  results,  is  soon  followed  by  a  change  of  form, 
whence  there  occurs  a  separation  into  distinct  layers  in  this 
membrane ;  take  for  example  one  of  the  meridians  of  the 
blastoderm  where  the  globules  become  multiplied  more  than 
in  any  other  place ;  here  the  blastoderm,  as  with  every  epi- 
thelium which  becomes  hypertrophied  in  a  certain  portion, 
is  obliged,  as  will  be  seen  later  in  the  formation  of  glands 
and  papillae,  to  swell  out  and  form  a  sort  of  pouch  on  which 
may  be  lodged  the  new  globules  that  are  formed.  This 
pouch  or  villosity  (Fig.  3  C)  is  the  first  rudiment  of  the 
embryonic  body.  Without  now  going  into  the  details,  it  is 
necessary  simply  to  mention  that  at  this  point  the  globules 
become  separated  into  three  layers  or  folds,  viz.,  the  external, 
internal,  and  intermediate  folds. 

The  external  fold^  called  the  corneal^  maintains  its  glob- 
ular condition,  and  from  this  is  formed  our  epiderm,  our 
external  cuticle,^  and  such  of  the  organs  as  may  be  derived 

*  A  comparison  of  the  two  kingdoms  demonstrates  the  fact 
that  both  animals  and  vegetables  have  an  external  envelope,  com- 
posed of  analogous  cells;  so  that  we  can  apply  to  each  the  name 
cuticle.  Yet  in  the  vegetable  the  cuticle  is  very  simple,  and  almost 
everywhere  the  same,  but  in  the  animal  it  is  complex,  and,  accord- 

*  A,  Vitelline  membrane.  B,  Simple  form  of  Blastoderm.  C.  Point  where 
the  Blastoderm  is  already  composed  of  three  layers  of  cells,  three  tolds. 

2 


18  GENERAL  PHYSIOLOGY. 

therefrom  (we  shall  see  farther  on  whether  the  nerve  glob- 
ules are  derived  from  the  external  or  the  intermediate  fold 
of  the  blastoderm). 

The  internal  fold  will  give,  by  means  of  the  envelopment 
which  forms  the  internal  cavity  of  the  embryo,  the  internal 
cuticle^  or  the  epithelium  of  the  future  intestinal  canal  of 
the  emljryo,  and  also  the  numerous  adjuncts  of  this  canal, 
most  of  the  glands,  and  also  the  lungs. 

The  globules  of  the  intermediate  folds  undergo  transfor- 
mations which  are  much  more  complicated ;  some  are  trans- 
formed, by  the  mechanism  already  mentioned  when  treating 
of  the  globules  in  general,  into  muscular,  nervous  (perhaps 
also  into  nerve  cells)  elastic,  and  connective  fibres,  and  other 
forms  of  the  connective  tissue ;  others  remain  in  the  condition 
of  globules,  though  changing  their  form ;  and  again  others 
become  fused  with  the  fibrous  elements  of  the  connective 
tissue  (embryonic  globules,  cells  of  cartilage,  of  bone  and  of 
tendons)  and  others  bathe  in  a  liquid  (blood  globules)  ;  thus, 
in  short,  the  intermediate  gives  origin  to  two  globular  forms, 
viz.,  the  embryonic  cell  and  the  blood  globule  (and  possibly 
the  nerve-cell.)  ^ 

The  elements  of  the  external  cuticle,  and  those  of  the 
internal  cuticle  or  internal  epithelium  being  then  united  in 
the  single  term  epithelial  (or  lining)  globules,  since  they  line 
the  surfaces^,  we  have  but  four  kinds  of  globules  to  study, 
viz.,  the  epithelial,  the  nerve,  the  blood,  and  the  embryonic 
globule. 

1.  Epithelial  globules,  placed  upon  fibrous  membranes, 
destined  only  for  their  support,  form  the  sole  living  portions 

ing  to  whether  it  covers  all  the  superficial  parts  of  the  body  or  the 
cavities  communicating  with  the  exterior,  it  is  either  internal  or 
external. 

1  This  distinction  of  the  blastodermic  cells  may  at  first  seem 
surprising,  though  a  similar  phenomenon  is  continually  passing 
under  the  observation  of  every  surgeon.  In  a  fresh  superficial 
wound,  there  appears  first  a  mass  of  globules,  primarily  alike, 
which  separate  themselves  so  as  to  become  either  epiderm-cells, 
connective  fibre,  etc.,  before  the  cicatrix  is  formed,  and  exactly  in 
the  same  way  as  in  the  folds  of  the  epiderm. 

2  In  fact,  the  word  "  epithelium  "  was  primarily  used  to  designate 
the  epiderm  of  the  nipple,  and  afterwards  to  designate  the  epiderm 
of  the  mucous  membrane,  to  which  there  is  now  a  tendency  to  limit 
its  application. 

Astruc  says :  "  La  peau  fine  et  delicate  qui  recouvre  le  mamelou, 
et  qu'on  appelle  Epithelion  "  (fTrt,  OrjKr] ;  upon,  the  nipple). 


mMmmmmmmM. 


DIFFERENT  KINDS  OF  CELLS.  19 

of   these    membranes,   and,   according  to    their    functional 
activity,'  they  present  differing  forms ;  if  they  are  situated 
in  a  region  where  their  functions  are  not  very  active  they 
are  few  in  number  and  in  order  to  occupy  completely  the 
surface  given  up  to  them,  they  are  flattened  out,  forming  a 
sort  of  pavement,  and  hence  are  called  pavement  (or  tessel- 
lated) ep^7Ae/mm  (Fig.  4,  A).   If,  ^ 
on  the  contrary,  as,  for  example,  c^^jrs-^r—^~-MS—t—7s-^c^:::y 
on  the  more  important  mucous 
membranes,  their  vital  functions  B 
are   very   active,   they    become    \^^^^J^Q^IoEPPJK 
multiplied,  accumulate  in  large 
numbers  upon  the  same  place, 
and  make  room  for  each  other, 
by  being  compressed  sideways ; 
and  so  instead  of  being  round 
they  become  cylindrical,  hence 
they  are  called  cylinder  (or  col-      ,^  _,      .    ^^^-/^  .«  ,. 

•^      .         .,,.    ^      ^f^-        4     r,\  Various  forms  of  Epithelium.* 

umnar)  epithelmm  (rig.  4,  B). 

Finally,  if  a  simple  layer  is  insufficient,  the  globules  are 

superposed,  and  hence  are  called  stratified  epithelium  (Fig. 

4,C). 

Moreover,  for  the  purpose  of  offering  a  large  surface  with- 
out occupying  too  much  space,  these  epithelium  cells  over- 
lap each  other,  an  instance  of  which  may  have  been  re- 
marked in  the  blastoderm,  and  according  to  whether  the 
overlapping  is  on  the  superficial  surface  or  on  the  side  near 
the  deeper  tissues,  these  make  up  papillae  or  glands ;  more 
particular  mention  will  be  made  of  this  subject  when  we  have 
occasion  to  speak  of  the  formation  of  the  epithelium  of  the 
mucous  membrane  of  the  mouth. 

The  functions  are  of  far  greater  importance  than  the  form 
of  the  epitheliums ;  these  may  be  divided  into  three  classes. 
Certain  of  the  globules  present  an  obstructing  surface  to  the 
passage  of  fluids,  &c.,  and  are  impermeable,  as,  for  instance, 
in  the  epithelium  of  the  bladder  and  of  the  serous  mem- 
branes in  general.     These  might  be  called  neutral  globules. 

Another  class,  on  the  contrary,  absorb  very  actively  the 
substances  (gas  or  liquid)  brought  in  contact  with  them,  and 
transport  these  to  the  more  distant  and  deeper  portions  of 
tissues,  as  is  done  for  instance  by  the  blood  globule.  These 
may  be  called  absorption  globules. 

*  A,  Pavement  epithelium.  B,  Columnar  epithelium.  C,  Stratified  epi- 
thelium. 


20  GENERAL  PHYSIOLOGY. 

A  third  class  possess  a  faculty  of  drawing  to  them  certain 
substances  contained  in  the  neighboring  tissues  or  fluids,  and 
thus  free  the  organism  from  which  these  are  detached.  In 
this  way  the  scaly  portions  of  the  epiderm,  before  passing 
into  this  condition  and  falling  off,  attract  certain  calcareous 
salts,  and  more  especially  the  phosphates  which  are  con- 
tained in  the  organism.  This  is  also  an  example  of  tlie 
functions  of  secretion,  and  these  are  called  secretion  globules. 
These  globules,  more  than  any  of  the  others,  are  characterized 
by  ephemeral  existence,  and  form  the  largest  portion  of 
glands ;  the  mammary  gland  is  nothing  but  a  membrane  of 
canaliculae,  covered  with  globules  which  possess  at  certain 
times  an  excessively  active  life ;  then  they  become  very 
rapidly  transformed,  and  their  remains  constitute  the  milk. 

2.  The  nerve  globules  (or  cells)  are  not  fixed  upon  sur- 
faces under  the  form  of  membranes,  they  are  hidden  in  the 
deeper  parts,  constituting  what  has  been  called  the  gray 
nerve-tissue.  By  direct  experiment  it  is  impossible  to  judge 
of  their  life.  Yet,  like  the  others,  these  globules  seem  to 
live,  and  are  nourished,  and  though  we  cannot  judge  de  visu 
of  their  transformations,  at  least  by  comparison  upon  the 
dead  body,  these  are  found  differing  in  appearance  and  age, 
some  being  smaller  and  transparent,  others  greater,  pale,  or 
filled  with  granulations,  thus  indicating  a  commencement  of 
their  decay.  Influenced  by  their  metamorphoses,  these  glob- 
ules, as  well  as  the  nerves  with  which  they  enter  into  commu- 
nication, are  electro-motor.  Indeed  it  is  these  prolongations 
or  nerve  tubes  by  which  the  nerve  globules  are  character- 
ized, and  which  give  them  their  stellate  form. 

3.  The  blood  globules,  whose  existence  is  best  known 
and  the  most  accessible  to  our  senses,  form  in  blood,  and 
consequently  in  the  body  about  one-twelfth  of  our  whole 
weight.  They  differ  from  the  preceding  globules  in  the  fixct, 
that  instead  of  having  a  fixed  place  they  course  through  the 
whole  organism;  their  discoid  shapes  render  their  transit 
easier,  and  during  their  course  they  are  continually  being 
transformed,  certain  of  them  perishing  in  order  to  give  room 
to  others.  During  this  nomadic  state,  the  blood  globule  is 
still  characterized  by  the  phenomena  of  repulsion  and  attrac- 
tion, changes  of  form  and  composition,  loading  itself  at 
certain  places  with  chemical  products,  which  seem  destined 
for  deposition  in  other  places. 

4.  The  embryonic  cells  are  so  called,  because  they  are  the 
same  in  the  adult  that  they  were  in  the  embryonic  stage; 


DIFFERENT  KINDS  OF  CELLS,  21 

distributed  in  the  midst  of  the  tissues,  they  continue  to 
serve  for  the  production  (the  periosteal  cell  continually 
forming  bone)  or  for  the  reparation  of  breaches  which  may 
have  accidentally  made  a  rent  in  or  destroyed  the  tissues ; 
hence  also  their  name  plasmatic  cells.  Some  of  these,  incertce 
sediSy  help  sometimes  by  means  of  the  circulation  to  nourish 
the  tissues  where  they  are  distributed,  and  then  are  seen  in 
star-shaped  form  with  anastomoses  of  their  prolongations ; 
the  cornea  offers  a  beautiful  illustration  of  this  distribution 
(Fig.  5). 

At  other  times  the  plasmatic  cells  undergo  a  sort  of  decay, 
by  accumulating  fat  in  their  interior,  and  thus  afford  adipose 
tissue;  in  this  condition  they  are  no  longer  susceptible  of 
undergoing  transformations;  they  are  so  to  speak  dead. 
But  most,  though  changing  form  and  becoming  almost  mum- 
mified (stellate  plasmatic  cells),  preserve,  in  their  latent  con- 


Fig.  5.* 

dition,  all  their  vital  characteristics,  ready  to  wake  up  if  the 
excitation  is  sufficiently  strong ;  in  this  way  they  can  furnish 
new  forms,  as,  for  instance,  cancer,  different  tumors,  and,  in 
general,  purulent  abscess  globules.  In  this  way  the  embry- 
onic cells  become  pathological. 

Supposing  now  that  we  are  familiar  with  the  different 
kinds  of  globules,  excepting  the  embryonic  globule,  we  can 
represent  them  in  a  diagram,  grouping  together  the  functions 
of  the  three  classes  of  globules. 

We  can  represent  the  organism  as  a  homogeneous  mass, 
more  liquid  than  solid,  on  the  surface  of  which  is  a  layer  of 

*  Section  of  cornea  cut  parallel  to  the  surface.  Stellate  corpuscles,  with  their 
anastomotic  prolongations  {Hia). 


22  GENERAL  PHYSIOLOGY. 

cortical  or  epithelial  globules  (AAA),  of  which  some  ab- 
sorb, others  excrete,  and  finally  others  are  impermeable  or 
neutral.  In  the  interior,  towards  the  middle  far  from  the 
surface  (Fig.  6,  B),  are  found  a  group  of  globules,  relatively 
permanent;  viz.,  the  nerve  globules,  which  by  means  of  their 
prolongations  are  in  communication  with  the  peripheral 
globules  so  as  to  be  excited  by  one  set  and  to  react 
upon  another  (reflex  actions).  Thus  the  blood  globules 
travel  from  the  periphery  towards  the 
centre,  and  vice  versa  (Fig.  6,  C  C) ; 
and  this  circular  current  draws  tow- 
ards the  centre  the  elements  of  nu- 
trition absorbed  by  certain  globule^ 
from  the  surface,  and  draws  the  de- 
cayed portions  of  the  globules  at  the 
centre  towards  the  globules  upon  the 
surface,  which  are  then  thrown  oif  (ex- 
Diagram  of '&e  organism*  cremental  secretions)  The  blood  glob- 
ule  thus  acts  as  a  medmm  oi  exchange, 
the  same  process  in  lower  animals  being  effected  by  imbibi- 
tion. 

Though  these  are  the  more  simple  forms  of  globular  activ- 
ity, yet  it  must  not  be  forgotten,  that  these  phenomena  are 
also  linked  with  those  belonging  to  chemistry  and  physics, 
which  likewise  should  be  studied  at  the  same  time ;  as  for 
instance  the  blood  globule  seems  to  be  of  service  to  the 
nerve  globule  by  establishing  for  purposes  of  nutrition  a 
communication  between  this  deep-seated  globule  and  those 
at  the  surface ;  but  its  circulation  requires  the  intervention 
of  the  nerve  globule,  which  may  excite  thd  muscular  fibre, 
and  thus  give  rise  to  certain  mechanical  phenomena  of  hydro- 
statics, etc. 

Now  it  may  be  noticed  that  the  collection  of  the  phenomena 
of  animal  life  constitutes  a  living  chain  that  must  be  artificially 
broken  for  convenience  of  study.  The  most  striking  phenom- 
ena is  the  wandering  of  the  blood  globule ;  it  might  most 
naturally  seem  that  the  commencement  of  our  study  should 
be  with  this  phenomenon ;  but  we  prefer  to  commence  first 
with  the  nerve  globule,  which  will  lead  us  to  study,  secondly, 
the  non-globular  forms  (muscles)  with  which  it  is  connected; 
and  subsequently  the  movements  and  other  mechanical  and 

*  A  A  A,  Globules  from  the  surface,  epithelium.  B,  Central  nerve-globules, 
with  prolongations  coming  from  or  going  to  the  suiface.  C  C,  The  cii'cle  of  cir- 
culation of  the  blood. 


DIFFERENT  KINDS  OF  CELLS.  28 

physical  phenomena  of  the  organism,  as  well  as  the  tissues 
which  are  its  seat.  Then  we  shall  consider  the  blood  globule 
and  its  circulation,  and  finally,  prepared  by  our  knowledge  of 
the  accessories,  we  can  more  readily  comprehend  the  more 
intricate  relations  of  the  internal  and  external  coverings,  and 
especially  the  epithelium  of  the  genital  organs,  as  well  also 
as  our  point  of  departure,  the  ovum. 


PART  SECOND. 


NERVOUS     SYSTEM. 


I.  Nervous  System  in  General. 

1.  Anatomical  Elements.  —  The  nerve  globule  partakes 

of  the  general  proper- 
ties of  the  living  glob- 
nle ;  its  dimensions 
are  very  small  (one  to 
eight-hundredths  of  a 
millimetre) ;  but  it  at- 
tains in  certain  regions 
larger  proportions,  and 
may  even  with  a  little 
care  be  seen  with  the 
naked  eye.  The  nerve 
globules  are  looked 
upon  as  cells  having  an 
envelope  (?)  enclosing 
protoplasmic  elements, 
a  nucleus,  and  a  nucle- 
olus. 

These  globuies  are 
generally  stellate,  that 
is  to  say,  provided  with 
prolongations  (Fig.  7) ; 
at  this  present  time 
globules  having  one 
eiobuiM,  their  proiongauons,     prolonffation  are  called 

clei,  and  nucleoli.*  •      t         .  i  i 

unipolar^  those  havmg 
two  prolongations,  striking  out  in   the  same  direction  or 

*  ffl.a,  From  the  deep  portion  of  the  gray  substance  of  the  convolutions  of  the 
cerebellum,  c?,  Cells  from  the  posterior  portion  of  the  gray  substance  of  spinal 
cord  (dorsal).    In  all  these  globules  the  prolongations  are  more  or  less  torn. 


NERVOUS  SYSTEM  IN  GENERAL. 


25 


oflener  in  opposite  directions,  are  bipolar  ;  but  most  of  them 
are  onulUpolar^  and  may  have  as  many  as  ten  prolongations. 
These  prolongations  are  ordinarily  quite  long,  and  constitute 
the  nerve  fibres.  (Fig.  8.) 
These  fibres  are  composed  of 
a  thin  envelope  {vv)  (forming 
Schwann's  sheath)  encircling 
a  medullary  substance  (mye* 
line,  mrn)  which  may  easily 
be  decomposed  into  little 
drops  of  fat,  and  in  the  centre 
of  this  a  thin  axis  cord  {a) 
discerned  with  difficulty,  the 
axis  cylinder.  Some  fibres 
may  be  reduced  to  simple 
axis  cylinder  and  to  the  pe- 
culiar sheath  of  Schwann 
without  any  medullary  sub- 
stance (fine  fibres  or  fila- 
ments). The  membrane  of 
Schwann  and  the  medullary 
sheath  serve  only  for  the  pro- 
tection and  isolation  of  the 
axis  cylinder.^  The  axis  cyl- 
inder thus  appears  to  be  the  most  important  part  of  the 
nerve  tube.  Finally  there  are  found  in  certain  nerves,  and 
especially  in  the  branches  of  the  great  sympathetic,  flat,  pale, 
or  amorphous  fibres,  rarely  fibrillary,  and  furnished  with  very 
distinct  nuclei  (Fig.  8,  A)  :  (gray  or  gelatinous  fasciculus)  ; 
these  are  the  fibres  of  Remak,  which  some  physiologists 
(Morel)  consider  as  belonging  to  the  connective  tissue, 
though  the  nerve  character  of  these  fibres  is  indicated  by 
the  history  of  the  development  of  the  nerve  fibre,  and  by  the 
study  of  the  pale  nerve  elements  in  the  lower  animals. 

^  Recent  histological  researches  by  Ranvier  appear  to  show  that 
the  nerve  tubes  are  formed  of  cells  joined  together  at  the  ends.  He 
has  also  ascertained  that  the  substance  of  Schwann  does  not  form 
a  continuous  cylindrical  axis,  as  has  been  hitherto  supposed,  but 
exhibits  at  regular  intervals  constrictions  in  the  shape  of  rings. 

*  A,  Gray  fasciculus,  gelatinous,  from  the  mesentery,  treated  by  acetic  acid. 

B,  White  primitive  fibre,  from  crural  nerve,    a,  Axis  cylinder  exposed.    v,v,  Fibre, 
with  its  medullary  sheath,  becoming  varicose  and  oozing  out  m  drops  at  w,7». 

C,  Primitive  fibre  from  brain,  containing  no  myeliue.    300  diam.    (Virchow 
"  Cellular  Pathology.")  ' 


Fig.  8.  —  Gray  and  white  nerve  fibres.* 


26 


NERVOUS  SYSTEM 


It  might  he  added  that  in  certain  little  trunks.,  isolated  from  the 
great  sympathetic  nerve  system,  the  number  of  these  pale  Jihres  is  so 
large.,  and  the  number  of  tubes  with  medullary  substance  so  small,  we 
are  obliged  (especially  in  the  splenic  nerves)  to  consider  Remak'S 
fibres  as  true  nerve  fibres. 

If  the8e  prolongations  of  the  nerve  globules  are  followed 
up  carefully,  the  nerve  tubes  will  be  observed,  after  a  shorter 
or  longer  distance,  to  be  connected,  in  fact  joined,  with  a 
neighboring  or  a  distant  globule,  or  sometimes  with  several 
of  these.  Thus  in  the  spinal  cord  there  are  globules  whose 
ramifications  connect  them  with  other  globules.  Sometimes 
the  nerve  fibres,  on  the  other  hand,  terminate  in  muscles 
(motorial  end-plates),  or  even  in  organs  which  are  at  present 
but  problematical  (tactile  bodies),  and  which  are  specially- 
found  in  the  skin.  It  may  also  be  noticed  that  generally 
nerve  fibres  are  only  commissures  or  bridges  projecting  from 


These  constrictions,  placed  at  distances  varying  according  to  the 
dimensions  of  the  tubes,  enclose  segments 
which  are  called  inter  annular  segments.  Each 
of  these  aj)pears  to  represent  a  cell;  indeed, 
in  the  centre  of  each,  and  on  the  inner  sur- 
face of  the  substance  of  Schwann  is  found  a 
flat  oval  nucleus  (Fig.  9)  floating  in  a  sea  of 
protoplasm,  with  which  the  tissue  is  lined. 
Farther  in  is  found  the  myeline,  which,  con- 
sidered in  regard  to  general  morphology, 
bears  the  same  relation  to  the  interannular 
segment  as  the  fat  in  an  adipose  cell  does  to 
the  cell.  The  signification  of  the  cylindri- 
cal axis,  which  runs  uninterruptedly  through 
the  whole  series  of  segments,  has  not  yet 
been  definitely  ascertained  from  the  stand- 
point of  general  morphology.  The  study 
of  the  degeneration  of  the  nerves  after  sec- 
tion, seems  to  confirm  the  foregoing  conclu- 
sions as  to  the  nature  of  the  interannular 
segments,  without,  however,  yielding  us  any 
more  precise  information  as  to  the  nature 
of  the  axis  cylinder,  which  is,  notwith- 
standing, the  essential  element  of  the  nerve 
tube.  Indeed,  it  seems  probable  that  the  other  appearS^nces  are 
simply  due  to  the  artificial  methods  used  in  the  preparations. 

*  A,  Nerve  tube  under  low  magnifying  power,  a,  Constriction,  b,  Nucleus 
of  interannular  segment,  c,  Axis  cylinder.  B,  The  constriction  and  part  of 
interannular  segment,  seen  under  a  higher  power  (prepared  with  osmic  acid). 
o/,  Constriction,    l/^  Nucleus  in  segment,    c,  lixterual  nucleus  in  sheath. 


Fig.  9. —Nerve  tubes,  ac- 
cording to  Banvier's  re- 
searches.* 


NERVOUS  SYSTEM  IN  GENERAL.  27 

a  nerve  globule  to  an  element  of  another  vaiiety,  or  simply 
to  another  nerve  globule. 

These  nerve  fibres  seem  to  be  only  a  physiological  sup- 
plement to  the  globule  from  which  they  originate;  every 
excitation  of  the  fibre  is  retained  by  the  globule,  and  vice 
versa :  the  fibre  disconnected  from  its  globule  undergoes  a 
degeneration  (fatty)  more  or  less  complete. 

2.  lAfe  of  the  I^ervous  System.  —  This  physiological  whole 
(globule  and  its  prolongations)  lives  and  is  nourished :  the 
nerve  centres,  composed  practically  of  globules,  need  an 
enormous  quantity  of  material,  and  give  back  to  the  sur- 
rounding media  (by  means  of  the  blood)  a  large  quantity  of 
refuse  matter.  The  mass  of  nerve  fibres  (nerves)  consumes 
likewise  some  materials,  and  produces  refuse  matter;  they 
in  other  words  are  fed;  they  are  very  vascular,  and  when 
the  supply  of  blood  is  shut  off,  phenomena  resembling  de- 
composition may  be  observed. 

It  will  be  noticed,  farther  on,  that  the  materials  consumed  by 
the  muscles  during  their  activity  are  principally  hydro-carbons 
(sugars  and  fats)  and  also  albuminoids  in  small  quantity.  On  the 
other  hand,  the  nerve  element  seems  to  require  albuminoid  sub- 
stances; and  the  more  intense  the  nerve  work,  the  greater  will  be 
the  amount  of  refuse  material,  caused  by  combustion  of  the  albu- 
minoids (especially  urea),  in  the  excretions,  in  the  urine,  and  in 
the  products  of  the  liver.  According  to  Biasson  (1868)  the  amount 
of  urea  excreted  by  man  varies  according  to  the  amount  of  cerebral 
activity.  Again,  Oscar  Liebreich  has  shown  that,  in  animals  who 
have  been  made  to  die  by  pain,  after  cutting  the  sensitive  roots  of 
one  side  of  the  sj)inal  cord,  this  side  (reduced  to  inertia)  would 
consume  less  protagon  than  the  other  side.  Protagon,  whose  com- 
position is  not  yet  defined,  seems  to  be  a  compound  of  fatty  phos- 
phates and  neurine^  and  serves  for  the  nutrition  of  the  nervous 
system,  to  which  it  is  carried  by  the  blood  globule.  According  to 
Austin  Flint,  Jr.,  the  excrementitial  product  formed  by  the  dis- 
assimilation  of  the  brain  and  of  the  nerves,  at  the  expense  of  prot- 
agon, is  represented  by  cholesterine,  which  is  separated  from  the 
blood  by  means  of  the  liver,  and  then  thrown  into  the  intestines. 
This  view  is  based  upon  a  number  of  experiments,  which  show, 
moreover,  that  the  excretion  of  cholesterine  is  in  direct  ratio  to 
the  nervous  activity.  The  common  expression,  "to  feel  bilious," 
seems  justified  by  one  of  the  elements  of  the  bile,  viz.,  cholesterine. 

These  acts  of  nutrition  produce  in  the  nerves  a  disengage- 
ment of  forces,  which  are  brought  to  light  by  electrical 
currents ;  this  phenomenon,  though  not  directly  observed  in 
the  nerve  globules,  is  very  evident  in  the  peripheral  nerves. 


28  NERVOUS  SYSTEM. 

In  the  state  ot  rest  certain  currents  are  constantly  travers- 
ing nerves,  going  from  the  surface  to  the  interior,  and  acting 
as  if  the  nerve  fibres  were  the  seat  of  two  enclosed  elements, 
the  extremity  being  positive  and  the  centre  negative.  In 
fact,  whenever  by  means  of  a  galvanometer,  a  communica- 
tion is  made  between  the  external  surface  and  the  surface 
of  the  section  of  a  nerve,  a  current  is  observed  to  pass  from 
the  periphery  towards  the  centre.  This  electrical  phe- 
nomenon, called  the  electro-motory  force  of  the  nerve,  disap- 
pears or  becomes  feeble  whenever  the  fibre  is  subjected  to  an 
irritation,  or  whenever  it  acts  as  a  conductor,  or  in  fact  when- 
ever it  performs  its  proper  function  ;  a  disappearance  of  the 
electro-motor  power  is  called  negative  oscillation.  It  has  been 
surmised  that  at  this  moment  nutrition  is  arrested,  and  with 
this  ensues  the  normal  current  of  a  state  of  rest.  The  de- 
duction can  easily  be  drawn  in  what  way  tha  fatigue  of  the 
nerve  may  be  brought  about,  and  why  an  irritation  too  long 
maintained  may  cause  destruction,  which  latter  may  also  be 
accompanied  with  pain. 

But,  on  the  other  hand,  direct  experiment  shows  that  the  nerve 
in  functional  activity  does  more,^ — there  is  produced  a  development 
of  heat,  the  existence  of  which  Schiff  has  just  demonstrated  in  the 
nerve-centres,  influenced  by  fear,  or  excitement  of  the  senses,  or 
from  every  cause  which  may  produce  cerebral  activity.  It  may  be 
that  the  negative  oscillation  indicates  that  electricity  of  the  nerve 
in  a  state  of  repose  is  transformed  i^to  heat  in  the  active  state. 
(In  regard  to  this  see  farther  on  an  analogue  of  the  negative  oscil- 
lation, in  the  study  of  the  muscles,  and  also  the  transformation  of 
one  force  mto  another  force.) 

3.  Action  of  the  Nervous  System.  —  "What  constitutes  the 

special  function  of  the  nerve 
apparatus,  both  fibre  and  cell  ? 
—  This  consists  essentially  in 
a  phenomenon  called  reflex. 
When  a  nerve  fibre  is  irri- 
tated, this  irritation  is  trans- 
mitted  to  globules  more  or 

T^.  *   ^^'  ^^'   a       «     *    less  distant,  and  from  the  lat- 

Diagram  of  a  simple  reflex  action.*     ^         ,         ^  •    i         i 

ter   to   the   peripheral   parts. 

Most  generally  this  irritation  is  upon  a  tactile  corpuscle  or 

*  1,  Surface  (epithelium).  2,  Muscle.  A,  Centripetal  fibre.  B,  Central  nerve 
cell.  C,  Centrifugal  fibre.  A,  B,  C,  form  the  nti-ve  arc,  which  presides  over  the 
reflex  action :  the  diastaltic  arc  of  Marshall  Hall.  A  represents  the  dsodic  fibre  ; 
B,  the  central  excito-motor ;  and  C,  the  txodic  fibre. 


NERVOUS  SYSTEM  IN  GENERAL,  29 

Bome  analogous  organ  (adjuncts  of  the  peripheral  surfaces) ; 
it  is  transmitted  by  a  centripetal  fibre  to  a  central  globule, 
which  reflects  this  by  a  centrifugal  fibre  to  another  organ 
more  or  less  peripheral,  as,  for  instance,  a  muscle  whose  con- 
traction may  be  thus  eflfected,  or  to  a  gland  which  then  pours 
out  its  secretion. 

Thus  fibres  perform  their  function  of  carrying  the  excita- 
tion towards  a  globule,  or  of  transmitting  it  from  the  globule 
to  the  periphery;  hence  the  names  centripetal  or  sensitive 
given  to  the  former  nerves,  and  centrifugal  or  motory  to  the 
latter.  This  name  should  indicate  merely  that  this  is  the 
sense  in  which  the  function  of  the  fibre  is  manifested  to  us, 
but  no  essential  diflerence  between  centripetal  and  centrif- 
ugal filaments  are  intended,  as  we  shall  soon  see  that  direct 
experiments  demonstrate  the  contrary. 

The  ofiice  of  the  globule  is  to  favor  the  transmission  of 
the  excitation  fi-om  one  to  another  fibre ;  oftentimes,  indeed, 
the  first  globule  reflects  its  action,  by  commissural  fibres, 
upon  one  or  several  other  globules  which  can  turn  the  action 
in  a  different  direction  again,  either  directly  upon  a  centrif- 
ugal fibre,  properly  so  called,  or  upon  some  fresh  nerve 
globules :  the  globular  elements  can  even  absorb  or  enfeeble 
the  action,  or  even  store  it  up,  as  it  were,  in  a  latent  state, 
and  send  it  off*  only  at  another  time,  when  influenced  by 
new  excitations.  Hence  we  see  that  reflex  centres  present 
very  complicated  phenomena,  becoming  at  one  time  centres 
of  diffusion,  and  again  of  co-ordination  of  movements,  of 
memory,  etc. ;  these  centres  can  be  also  the  seat  of  sensation 
for  the  peripheral  excitations. 

Leaving  out  of  mind  the  central  phenomena  that  are 
difficult  of  analysis,  we  see  that  the  office  of  the  nerves  is 
essentially  that  of  conduction.  Now  what  constitutes  con- 
duction, and  what  is  the  peculiar  phenomenon  by  which  it  is 
characterized  ?  For  a  long  time  this  was  supposed  to  resem- 
ble and  partake  of  the  nature  of  the  electric  current ;  but  at 
the  present  time  it  is  proved  that  the  nerve  influx  has  nothing 
to  do  with  electricity.  In  the  first  place  its  rapidity  of 
propagation  has  been  calculated  to  be  28  to  30  metres  to  the 
second,  a  very  different  rate  from  that  of  the  electric  cur- 
rent, and  even  this  varies  with  the  temperature  of  the  nerve  ; 
according  to  Helmholtz,  in  frog's  nerve  cooled  to  a  tempera- 
ture of  the  freezing  point  of  water  (0^  c),  the  rapidity  of  the 
nerve  agent  is  but  one-tenth  of  what  it  is  at  15°  or  20° 
higher.    Again,  when  the  nerve  performs  its  functions,  in- 


30  NERVOUS  SYSTEM. 

stead  of  producing  electricity,  there  is,  on  the  contrary, 
negative  oscillation  (as  has  been  before  remarked),  that  is 
a  weakness  or  disappearance  of  the  normal  current  of 
repose. 

In  a  nerve  displaying  activity,  there  appears  to  be  a  sort 
of  molecular  vibration  which  is  propagated  from  point  to 
point  at  the  rate  of  28  to  30  metres  to  the  second.  This 
molecular  vibration  extends  both  ways  along  the  nerve; 
when  the  stimulus  is  applied  midway,  its  existence  is  evi- 
dent only  at  the  nervous  extremity,  where  an  organ  suitable 
for  its  reception  may  be  found  ;  as,  for  instance,  towards  the 
central  end  for  sensitive  nerves,  and  at  the  surface  or  pe-riph- 
ery  for  the  motor  nerves.  Thus  it  may  be  noticed  that 
the  terms  centripetal  and  centrifugal  depend  upon  the  dif- 
ferent connections,  and  that  both  can  conduct,  indifferently, 
either  way  (Vulpian). 

4.  Excitants  of  the  Nervous  System.  —  Those  excitants 
which  can  set  in  motion  the  functions  of  the  nerves  are 
numerous.  Some  of  these  are  chemical,  such  as  acids, 
ammonia,  &c. ;  these  agents,  it  will  be  seen,  excite  likewise 
the  muscles,  but  in  this  case  they  need  not  be  so  concen- 
trated as  in  the  former.  Others  may  be  in  the  nature  of 
mechanical  or  physical  excitants ;  as,  for  instance,  a  blow, 
electricity  or  heat.  Electricity  seems  to  excite  the  nerves 
only  by  the  sudden  changes  it  produces  in  their  molecular 
condition ;  thus  a  current  applied  to  a  nerve  affects  its  ac- 
tion, only  when  it  begins  or  terminates  its  passage  through 
the  nerve;  during  its  passage  no  action  is  evident.  In 
order  to  excite  nerves,  sudden  electrical  discharges  must  be 
applied,  and  this  is  the  reason  for  the  employment  of  an 
induced  current,  frequently  interrupted.  At  each  interrup- 
tion, there  ensues  an  excitation  of  the  nerve.  In  normal 
physiological  conditions,  the  external  excitors  are  brought  to 
bear  upon  the  ends  of  the  so-called  sensitive  nerves ;  certain 
of  the  peripheral  organs  of  this  class  (organs  of  special 
sense)  exist  where  particular  agents  (light,  sound,  heat, 
odors,  &c.),  give  rise  to  special  excitations. 

Finally,  the  central  organs  act  as  physiological  excitants  in 
the  reflex  order,  where  they  only  transmit  previously  received 
excitations,  and  in  the  phenomena  called  voluntary  (which 
are  doubtless  a  more  or  less  complex  form  of  reflex  actions). 
This  is  due  to  the  power  which  the  nerve  globules  possess  of 
storing  up  certain  excitations  (memory),  whose  manifesta- 
tions they  allow  only  at  a  given  time.     We  may  perhaps 


GENERAL  PHYSIOLOGY.  31 

suppose  that  the  central  nerve  globules,  by  the  simple  effect 
of  their  nutrition,  and  without  excitation  coming  from  out- 
side the  body,  are  capable  of  setting  free  forces  which  act 
upon  the  fibres;  this  property  has  been  called  automatism 
of  the  nerve  centres  (will,  muscular  tone  ?) 

5.  Excitahility  of  the  Nerve  Elements.  —  The  excitabil- 
ity of  the  nerve  elements,  especially  if  a  nerve  used  for 
experimental  researches,  may  vary  under  many  circum- 
stances. Heat  increases  this  up  to  a  certain  point:  cold 
diminishes  it.  Certain  medicinal  agents,  as,  for  instance, 
strychnine,  have  the  power  of  exciting  the  reflex  properties 
of  the  nervous  centres ;  others,  like  the  bromide  of  potas- 
sium, enfeeble  these  properties.  Woorara  {curare),  on  the 
other  hand,  seems  to  act  especially  upon  the  motory  termi- 
nations of  the  nerves,  and  there  to  arrest  the  power  of 
transmission,  for  it  is  hardly  reasonable  to  suppose  that  it 
would  act  upon  the  motory  nerves,  and  not  upon  the  sensory 
nerves;  this  would  show  that  these  two  kinds  of  nerves  have 
no  different  characters. 

Electricity  acts  at  the  same  time  both  as  an  excitant  and 
as  a  modifying  agent  of  excitability  to  a  nerve;  in  fact, 
when  a  current  is  applied  to  a  nerve,  excitability  is  increased 
at  the  negative  pole,  and  diminished  at  the  positive  pole, 
a  phenomenon  more  especially  described  under  the  head 
of  electro-tonus. 

But  the  excitability  of  a  nerve  is  especially  dependent  on 
its  nutrition.  Every  nerve  tube  separated  frpm  a  central 
living  organ  undergoes  fatty  degeneration  and  ceases  to 
be  excitable  at  the  end  of  a  few  days.  Absolute  rest  pro- 
duces the  same  effect,  for  the  function  is  necessary  to  the 
maintenance  of  life  and  of  nutrition;  per  contra,  the  exag- 
gerated excitations  produce  momentarily  the  weakening  of  a 
nerve,  which  must  needs  recover  its  strength  by  rest,  and 
we  have  remarked  that  excitation  of  the  nerve  modifies 
temporarily  the  phenomena  of  nutrition. 

II.   General  Physiology  of  the  Nerve  Centres. 

For  a  long  time  the  point  of  departure  of  the  nervous  sys- 
tem was  a  matter  of  ignorance :  the  size  and  position  of  the 
brain  led  the  ancient  physiologists  to  consider  that  as  the 
principal  centre  of  the  nerve-substance:  the  spinal  cord  was 
to  them  but  a  collection  of  nerves  ending  at  the  brain.  The 
minute  study  (histology)  of  the  gray  axis  of  the  spinal  cord 


32  NERVOUS  SYSTEM. 

and  the  physiological  experiments  of  Legallois  lead  us  now  to 
consider  the  spinal  cord  as  the  principal  nerve-centre  of  the 
organism.  Experimental  researches  have  been  principally 
concerned  with  the  spinal  cord,  and  the  characteristics  dis- 
covered here  have  been,  reasoning  by  analogy,  extended  to 
other  portions  of  the  nervous  system. 

Nerve  Centre^  Gray  Matter^  Nerve  Commissures.  —  In  the 
actual  state  of  our  knowledge,  the  three  principal  objects  in 
the  central  nerve  masses  are :  the  brain,  the  spinal  cord,  and 
the  small  nerve  centres  called  ganglia  (system  of  the  grand 
sympathetic)  distributed  through  the  visceral  cavities ;  these 
latter  have  slight,  if  any,  connection  with  the  brain.  But  the 
exact  notions  that  we  possess  are  applied  almost  exclusively 
to  one  of  these  objects;  viz.,  the  spinal  cord  and  its  ence- 
phalic portion  (bulb,  protuberance). 


Fig.  11.  —Transverse  section  of  the  spinal  cord  in  man.* 

From  an  anatomical  point  of  view  the  central  portions  are 
characterized  by  the  presence  of  nerve-cells;  but  from  a 
physiological  point  of  view  they  are  characterized  by  the 
reflex  act. 

Nerve  globules  of  the  spinal  cord  form  in  this  organ  a 
central  continuous  mass  (gray  substance,  gray  axis)  stretch- 
ing from  one  end  of  the  organ  to  the  other.     (Fig.  11.)     But 

*  Cervical  region  (10  diameters),  f^  Posterior  columns,  u,  Gelatinous  sub- 
stance of  the  posterior  horn,  k,  Postenor  root.  ?,  Anterior  roots,  a,  Anterior 
median  fissure,  c,  Posterior  median  fissure,  b,  Central  canal  of  tfie  cord,  g.  An- 
terior horns,    h,  Posterior  horns,    e,  Autero-lateral  column. 


GENERAL  PHYSIOLOGY. 


33 


if  anatomy  places  the  upper  bounds  of  the  spinal  cord  at  the 
point  of  the  occipito-atloidean  articulation,  the  physiologist 
extends  the  spinal  cord  to  the  interior  of  the  cranium,  as  well 
as  along  the  vertebral  canal,  and  even  as  far  as  the  sella 
turcica^  where  it  ends  with 
the  pituitary  body  (bulb, 
protuberance,  cerebral  pe- 
duncles, gray  matter  of  the 
third  ventricle.)  (Fig.  12.) 
In  the  encephalie  mass, 
properly  so  called,  the  nerve 
globules  are  distributed  in 
isolated  layers,  and  form  a 
number  of  islets.  These 
masses  are  placed  above 
the  cephalic  extremity  of 
the  spinal  cord,  and  form  in 
this  place  series  of  trans- 
verse bands.  Near  the 
place  where  the  spinal 
cord  bends  before  termi- 
nating in  the  sella  turcica 
are  found  a  number  of 
isolated  little  groups  of 
globular  matter.  They 
form,  in  a  manner,  sepa- 
rated stages  in  the  cranial 
cavity,  and  are  placed  in 
concentric  layers  one  upon 
the  other.  (Fig.  12,  D.) 
These  stages  have  received 
different  names ;  the  most 
superficial  of  them  is  in  con- 
tact with  the  skull,  and 
appears  in  the  form  of  an 
undulating  surface  envel- 
oping the  whole,  and  is  called  the  cortical  substance  of  the 
encephalon.  (Gray  substance  of  the  cerebral  convolutions. 
Fig.  12,  E,  E.)  Between  this  and  the  encephalic  prolonga- 
tion of  the  spinal  cord  (A)  are  found :  two  important  groups 

*  A,  A,  A,  Spinal  cord,  with  its  commissures.  B,  Region  of  the  protuber- 
ance. C,  Cerebellum.  D,  Thalami  optici  and  corpora  striata.  E,  E,  Gray- 
matter  (cortical  substance)  of  the  cerebral  convolutions,  a,  a,  a,  Anterior  roots. 
P,  P,  P,  Posterior  roots. 


Fig.  12. 
Plan  of  the  central  nervous  system. 


34  NERVOUS  SYSTEM. 

(D),  the  corpora  striata  in  front,  and  the  thalami  optid 
behind.  Finally,  in  the  posterior  portion  of  the  encephalic 
mass,  the  cerebelhim  reproduces  on  a  small  scale  the  preced- 
ing disposition.  (Fig.  12,  C.  Gray  convolutions  and  rhom- 
boid body  of  the  cerebellum.) 

We  know,  moreover,  that  the  prolongations  start  from  the 
nerve  globules,  which  thus  unite  them  to  each  other ;  in  this 
way  a  group  of  these  prolongations  form  a  communication 
in  the  brain  between  the  supei^ficial  and  the  inner  layer  of 
the  globules,  thus  constituting  the  corona  radiata  {fibrous 
C07ie) ;  lying  deeper  the  thalamios  opticus^  or  the  corpus 
striatum^  uniting  the  middle  with  the  lowest  layer. 

The  same  plan  holds  in  the  cerebellum.  Collections  of 
nerve  prolongations  stretch  from  one  portion  of  the  surface, 
or  cortical  layer,  to  the  rhomboid  body  {corpus  dentatum) 
of  the  cerebellum,  then  from  the  latter  to  the  other  portions 
of  the  encephalon  and  spinal  cord  {pedunculi  cerebelli,  sepa- 
rated into  superior,  middle,  and  inferior).  In  brief,  the 
encephalon  is  a  very  complex  system  of  little  continents  of 
gray  or  central  nerve  substance,  intercommunicating  with 
themselves  and  spinal  cord  by  numerous  commissures. 

The  spinal  cord,  likewise,  presents  similar  commissures; 
but  in  this  case  they  are  generally  longitudinal,  and  surround 
the  gray  centre  of  the  spinal  cord  with  an  envelope  of  white 
substance  (antero-lateral  and  posterior  columns),  and  then 
make  a  communication  from  one  globule  to  another  in  the 
spinal  cord,  and  again  between  these  globules  and  the  brain 
mass. 

Among  these  different  globules  of  the  centres  there  are  no 
communications  except  with  these  commissures :  they  simply 
communicate  with  each  other.  There  are  other  communica- 
tions, placed  outside  of  the  nerve  centres,  with  the  peripheral 
parts,  by  means  of  nerves  in  the  true  sense  of  the  word. 
The  spinal  canal  (spinal  or  rachidian,  and  cephalic  portions) 
alone  seems  to  possess  the  property  of  establishing  outside 
communications  with  the  different  organs  of  the  economy. 
All  the  fibres  to  be  met  with  in  the  cerebruna  or  cerebellum 
are  doubtless  real  commissures,  and  only  in  an  indirect  way, 
by  the  mediation  of  the  cord,  can  the  peripheral  nerves  be 
made  to  accord  with  the  encephalic  centres,  in  order  either  to 
produce  the  sensations  (centripetal  nerves),  or  to  bring  into 
action  the  property  of  volition  (centrifugal  nerves). 


SPECIAL  PHYSIOLOGY.  35 


in.   Special  Physiology  of  the  Nervous  System. 

A.  Peripheral  nerves. 

The  physiology  of  the  nerves  which  go  from  the  brain  to 
the  spinal  cord  has  been  a  very  engrossing  and  laborious 
study ;  minute  dissections,  experiments  on  animals,  pathologi- 
cal observations  studied  in  man,  have  been  alternately  used 
to  prove  the  functions  of  each  nervous  filament,  and  yet, 
especially  for  the  cranial  nerves,  science  has  not  yet  accom- 
plished any  degree  of  desirable  precision.  We  can  only 
here  briefly  indicate  the  principal  results  of  physiological 
researches,  which,  for  the  cranial  nerves,  can  be  understood 
only  by  an  exact  knowledge  of  the  complicated  topography 
of  this  portion  of  the  nervous  system. 

1.  Cranial  Nerves.  —  The  twelve  nerves  which  originate 
from  the  encephalic  portion  of  the  nerve  centres  (base  of  the 
brain,  protuberance,  bulb)  preside  over  the  general  sensibility 
or  the  special  sensibility,  or  the  movements  of  those  parts  to 
which  they  are  distributed;  they  may  preside  over  either 
one  of  these  functions  exclusively,  or  be  composed  of  different 
fibres  (mixed  nerves),  some  of  which  are  sensitive,  others 
motor. 

Olfactory  Nerve  (1st  pair). — This  nerve  appears  to  preside 
solely  over  the  special  sensibility  that  produces  the  sensation 
of  smells ;  we  say  appears,  because  CI.  Bernard  has  compiled 
a  number  of  observations  (and  specially  in  the  case  of  Marie 
Lemens),  where  the  complete  absence  of  the  olfactory  nerves, 
determined  at  the  autopsy,  was  not  marked  during  life  by  an 
absence  of  the  sense  of  smell.  Magendie  often  confounded 
the  special  sensibility  of  the  functions  of  the  olfactory  nerve 
with  the  general  sensibility  that  the  trigemini^rnish  to  the 
olfactory  mucous  membrane. 

Optic  Nerve  (2d  pair).  —  This  is  a  nerve  of  special  sensi- 
bility, and  carries  to  the  brain  the  impressions  of  light  received 
by  the  retina  {vide  organs  of  the  special  senses) ;  also,  every 
excitation  (section,  compression,  etc.)  of  the  optic  nerve  pro- 
duces no  sensation  of  pain,  but  simply  an  impression  of  light. 
The  incomplete  decussation  (chiasma)  of  the  optic  nerves 
seems  to  explain  single  vision  when  both  eyes  are  used. 
Indeed,  this  arrangement  is  such  that  the  left  optic  tract,  for 
instance,  divides  at  the  point  of  the  chiasma,  so  that  botli  the 
right  and  the  left  optic  nerve  form  the  left  halves  of  both 
retinaB  (the  outer  half  of  the  left  retina  and  the  inner  half  of 
the  right  retina). 


8b  NERVOUS  SYSTEM. 

An  object  placed  at  the  right  would  thus  be  perceived 
solely  by  means  of  the  left  optic  tract,  if  we  bear  in  mind  the 
points  of  the  two  retinae  upon  which  its  image  would  be  de- 
picted (so-called  theory  of  coincident  points ;  for  all  the 
points  of  the  left  half  of  a  retina,  coincident  points  are  found 
in  the  left  half  of  the  other,  and  inversely.)  We  shall  see 
when  studying  the  retina,  that  this  explanation,  originating 
with  Wollaston,  loses  much  of  its  importance  in  the  consid- 
eration of  clear  or  distinct  vision  where  the  two  images  of 
the  object  would  be  depicted  on  the  macula  lutea  (yellow 
spot)  of  each  eye. 

The  optic  nei-ve  conveys  luminous  sensations  towards  the 
tuhercula  quadrigemina. 

Motor  Nerve  of  the  Eye  (3d  pair,  motor  oculi). — 
This  nerve  is  solely  motor;  it  affords  movement  to  those 
muscles  to  which  it  is  distributed,  namely,  to  the  levator  pal- 
pebraB  (elevator  of  the  eyelid),  the  superior  internal  and 
inferior  straight  muscles,  and  to  the  inferior  oblique ;  also  by 
means  of  the  motor  rootlet  which  it  furnishes  to  the  ophthal- 
mic (or  lenticular)  ganglion,  this  nerve  innervates  (furnishes 
nervous  power)  to  the  muscles  of  the  pupil  (constrictor)  and 
of  the  choroid  (apparatus  for  accommodation). 

Thus  when  this  nerve  is  cut,  or  compressed  by  a  tumor, 
the  following  symptoms  may  be  noted,  and  in  this  way,  the 
physiology  of  the  common  motor  nerve  of  the  eye  may  be 
summed  up,  and  a  priori  its  anatomical  distribution  be  de- 
duced :  1st,  Exophthalmia ;  2d,  Closing  of  the  upper  lid ; 
3d,  External  strabismus;  4th,  Inability  to  rotate  the  eye 
when  the  head  is  inclined  on  the  opposite  side  of  that 
in  which  the  lesion  is  situated,  or,  moreover,  according  to 
recent  researches,  when  the  vision  is  directed  obliquely 
from  above  outwards,  or  to  the  external  side  of  the  body 
(Bonders).  There  is,  then,  diplopia  with  images  crossed ; 
the  image  furnished  to  the  diseased  side  is  inclined  from  this 
side,  and  is  placed  higher  up  than  the  image  furnished  by  the 
healthy  side;  5th,  Dilatation  of  the  pupil;  6th,  Inability  to 
adapt  the  eye  for  short  distances. 

Patheticus  (4th  pair,  nervus  trochlearis). — This  nerve 
innervates  the  upper  oblique  muscle;  it  presides  over  the 
movements  of  rotation  and  of  oblique  vision.  When  it  is  cut 
or  pathologically  destroyed,  symptoms  just  the  opposite  of 
those  we  have  noted  as  No.  4  (see  above),  in  the  paralysis  of 
the  common  motor  are  observed. 

Motor  Omli  Externus  (6th  nerve).  —  This  nerve  inner- 


SPECIAL  PHYSIOLOGY.  37 

vates  the  external  straight  muscle,  and  presides  over  the 
movements  outwards ;  its  destruction  consequently  involves 
an  internal  strabismus. 

Trifacial  (5th  pair,  or  nervus  trigeminus). — This  nerve 
is  composed  (two  roots)  of  centripetal  (sensitive)  and  of 
centrifugal  fibres  (motory  or  secretory). 

Certain  fibres  have  been  named  trophic,  but,  as  there  is  a 
good  deal  of  discussion  in  regard  to  their  existence,  it  is 
hardly  worth  while  to  consider  these  in  this  work ;  disturb- 
ance of  nutrition  (trophic)  observed  after  section  of  the  tri- 
facial, as  well  as  of  many  other  nerves,  is  dependent  on  loss 
of  sensation  to  external  injuries  (Snellen),  or  to  vaso-motor 
disturbances  (Schiflf).  These  fibres  are  distributed  through 
the  three  branches  of  the  trifacial. 

The  opthalmic  nerve  (or  first  division  of  the  fifth  pair) 
presides  over  sensation  in  the  skin  of  the  forehead,  of  the 
root  and  back  of  the  nose,  of  the  upper  eyelid,  over  the  sen- 
sation in  the  conjunctiva,  of  the  cornea,  of  the  iris,  and  even 
of  the  retina  (general  sensibility  by  means  of  the  central 
nerve  of  the  retina).  It  furnishes  secretory  fibres  to  the  lach- 
rymal gland. 

The  superior  maxillary  nerve  presides  over  sensation  of 
the  lower  eyelid,  of  the  cheek,  of  the  wing  or  side  of  the  nose, 
of  the  upper  lip,  of  the  nasal  mucous  membrane  (general  sen- 
sibility), of  the  teeth  of  the  upper  jaw,  etc.  It  furnishes 
secretory  filaments  to  the  glands  of  these  different  regions, 
and  particularly  to  the  glands  of  the  olfactory  mucous  mem- 
brane. The  motor  branches  which  it  appears  to  send  off  are 
but  fibres  of  reflexion  that  come  from  the  facial  by  a  very 
complicated  path  (large  superficial  petrosal  of  the  vidian 
nerve). 

The  inferior  maxillary  nerve  presides  over  the  sensation 
of  the  teeth  of  the  lower  jaw,  of  the  skin  of  the  chin,  of  the 
lower  lip,  of  the  auriculo-temporal  region,  of  the  buccal  and 
lingual  mucous  membrane  \  it  moreover  presides  over  the 
special  sensibility  of  the  anterior  half  of  the  tongue  (sense  of 
taste),  and  the  lingual  nerve  (lingual  branch  of  the  fifth 
pair)  is  generally  considered  as  the  nerve  of  this  special  sense. 
Though  the  chorda  tympani  may  be  concerned  in  the  sense 
of  taste,  yet  in  all  cases,  gustatory  nervous  filaments  are  sent 
off  by  the  trifacial,  but  by  a  complicated  path  which  is  not 
yet  settled  by  physiologists  (Lussana,  Schiff ).  This  nerve 
furnishes  motory  fibres  to  all  the  muscles  of  mastication,  some 
of  which  (masseter,  temporal,  pterygoids)  elevate  the  jaw, 


88  NERVOUS  SYSTEM. 

and  others  (mylo-hyoid  and  the  anterior  belly  of  the  digas- 
tric) depress  the  jaw,  perhaps,  also,  t©  the  stapedius  and  to 
the  intei-nal  muscle  of  the  malleus;  but  these  last-named 
filaments  appear  to  be  mostly  branches  belonging  to  the  facial, 
as  well  as  to  the  secretory,  filaments,  which  go  to  the  sub- 
maxillary, sublingual  (chorda  tympani),  and  parotid  glands. 

Summing  up,  it  will  be  seen  that  the  trifacial  nerve  essen- 
tially presides  over  the  sensibility  of  the  three  grand  divisions 
of  the  face  (forehead,  cheeks,  and  chin),  whence  the  name 
trigeminus  or  trifacial. 

Facial  Nerve  (portio  dura  of  the  7th  pair).  —  This  is 
essentially  a  centrifugal  nerve  (motory  and  secretory)  ;  the 
secretory  functions  devolve  apparently  on  the  intermediary 
nerve  of  Wrisberg  (CI.  Bernard).  The  facial  receives  some 
sensory  anastomoses  which  proceed  to  it  from  the  pneumo- 
gastric  and  trif  icial  nerves. 

By  its  terminal  branches  this  nerve  presides  over  the 
movements  of  all  the  cutaneous  (peauciers)  muscles  of  the 
head,  from  the  frontal  to  the  occipital,  comprising  among 
these  the  buccinator,  and  even  to  the  cutaneous  muscle  of 
the  neck.  Through  its  filaments,  whose  path  is  as  compli- 
cated as  the  windings  of  the  aqueduct  of  Fallopius,  whose 
canal  it  follows,  it  presides  over  the  secretion  from  the  dif- 
ferent salivary  glands,  the  contraction  of  the  muscles  con- 
cerned in  the  first  intervals  of  deglutition  (velum  palati, 
styloid  muscles,  posterior  belly  of  the  digastric,  etc.),  as  well 
as  the  contractions  of  the  muscles  of  the  middle  ear  (tensor 
tympani,  or  musculus  internus  mallei,  and  stapedius).  Lon- 
get  regards  the  branches  given  ofi"  to  these  last  two  muscles 
as  being  the  continuation  of  the  intemiedia/ry  of  Wrisberg^ 
which  he  names  consequently  motory  tympanic  nerve. 

By  the  above  physiological  notions,  it  is  explained  why 
paralyses  of  the  facial  nerve,  arising  from  superficial  causes, 
are  characterized  only  by  distortion  of  the  features,  whilst 
those  from  deep-seated  causes  involve,  in  addition,  a  certain 
difficulty  of  deglutition  (deviation  of  the  uvula,  etc.)  as  well 
as  of  hearing. 

Auditory  Nerve  (portio  mollis  of  the  7th  pair).  —  This 
is  the  special  nerve  of  the  organ  of  hearing.  Its  irritation  can 
only  occasion  sensation  of  sounds;  its  section  is  followed  by 
complete  deafness.  Its  partial  section  in  experiments  on  ani- 
mals cause  movements  of  rotation  (Flourens)  that  have  been 
explained  as  caused  by  a  vertigo  of  the  senses  (Gratiolet, 
Vulpian). 


SPECIAL  PHYSIOLOGY.  39 

Glosso-pharyngeal  Nerve.  —  This  is  a  mixed  neiTe  even 
fi'om  its  origin  (Mueller,  Bernard) ;  however,  Longet  consid- 
ers this  primarily  a  sensory  nerve,  possessing  no  derived 
motor  filaments.  If  experiments  on  animals  do  not  always 
allow  of  the  determination  of  motory  properties  (Jolyet),  still 
the  existence  of  these  can  be  deduced  from  the  rapidity  with 
w^hich  these  lose  their  power  of  excitability  (Biffi,  Morganti, 
Schiflf).  The  glosso-pharyngeal  presides  over  the  move- 
ments of  the  pharynx,  (as  also  the  facial,  pneumo-gastric,  and 
spinal),  over  the  general  sensibility  of  the  region  of  the 
fauces,  of  the  base  of  the  tongue,  and  finally  over  the  special 
or  gustatory  sensibility  of  the  base  of  the  tongue  (see  organs 
of  special  sense,  taste). 

Pneumo-gastric  (nervus  vagus,  par  vagum). — BischoflTand 
Longet  are  unwilling  to  admit  in  the  roots  of  this  nerve  any 
other  than  sensory  filaments ;  still  experiments  by  Bernard, 
Van  Kempen,  Vulpian,  and  Jolyet  prove  that  the  pneumo- 
gastric  is  both  motory  and  sensory,  from  its  origin ;  it  is  also 
true  that  it  receives  a  large  number  of  motory  anastomoses 
from  the  neighboring  nerves. 

The  very  complicated  physiology  of  this  nerve,  taking 
into  consideration  its  very  complex  anatomical  distribution, 
is  found  to  vary  with  each  organ  to  which  its  branches  are 
sent  ofi*  (see  circulation,  digesdon,  and  respiration).  We 
can  here  only  generalize  upon  these  functions.  The  pneumo- 
gastric  might  be  called  a  mixed  tri-visceral  nerve,  or,  in  other 
words,  it  affords  sensibility  and  movement  to  three  great 
viscera  (heart,  lungs,  and  stomach),  and  also  to  their  appen- 
dages. But  it  must  be  remembered  that  the  sensibility 
afforded  by  this  nerve  is  generally  obtuse,  and  in  no  wise 
localized,  and  gives  vague  sensations  of  the  kind  called 
general  (see  farther  on ;  physiology  of  the  encephalon),  or 
may  give  rise  to  reflected  actions  of  which  the  mind  is  un- 
conscious. Consequently  the  movements  over  which  it  pre- 
sides are  mostly  reflex,  and  but  slightly  under  the  power  of 
the  will. 

In  the  apparatus  for  respiration.,  the  pneumo-gastric  af- 
fords sensibility  to  the  glottis,  the  trachea,  and  the  lung  (the 
centripetal  conductor  of  the  desire  of  breathing)  ;  also  motion 
to  the  glottis  (movements  of  respiration  and  not  of  phona- 
tion.  CI.  Bernard) ;  also  to  the  smooth,  muscular  fibres  of 
the  trachea  and  bronchi  (Williams,  Paul  Bert). 

In  the  central  apparatus  for  circulation.,  it  gives  sensory 
and  moderating  cardiac  nerves  (see  circulation). 


40  NERVOUS  SYSTEM. 

In  the  digestive  apparatus^  it  furnishes  sensibility  to  the 
pharynx,  oesophagus,  and  stomach,  as  well  as  motion  to  these 
same  parts,  and  perhaps,  also,  to  the  small  intestine. 

[According  to  Legros  and  Onimus,  electrization  of  the 
pneumo-gastric,  with  interrupted  currents  (faradization), 
arrests  intestinal  movements,  and  arrests  these  not  in  a  state 
of  contraction  but  of  relaxation.] 

Finally,  it  presides  over  the  secretion  of  the  glands  of 
the  trachea  and  bronchi,  and  perhaps,  also,  the  glands  of 
the  stomach ;  however,  in  this  connection,  the  experi- 
ments are  contradictory  and  even  less  conclusive  concern- 
ing these  last-named  points;  the  same  holds  true  with 
regard  to  the  formation  of  sugar  in  the  liver ;  these  fibres, 
according  to  CI.  Bernard,  seem  to  be  centripetal ;  by  means 
of  their  peripheral  extremities  located  in  the  lungs  they  would 
excite  reflexively  those  nerves  tending  to  the  formation  of 
sugar  (vaso-motor?  ). 

Spinal  Accessory  Nerve. — This,  considered  by  Bischoffand 
Longet  as  accessory  (motoiy  portion)  to  the  pneumo-gastric, 
is,  in  a  physiological  point  of  view,  the  especial  antagonist  of 
the  pneumo-gastric,  since  it  presides  over  the  movements  of 
phonation,  almost  all  of  which  are  opposed  to  the  respiratory 
movements,  strictly  speaking,  as  well  in  the  glottis  (internal 
branch  of  the  spinal  nerve)  as  in  the  thorax  (external 
branch)  (CI.  Bernard).  Special  indications  are  also  found 
in  the  study  of  phonation,  which  lead  to  the  consideration  of 
the  spinal  as  a  nerve  of  phonation  and  of  mimicry. 

hypoglossal  (9th  pair).  —  This  is  exclusively  a  motory 
nerve  for  the  tongue  and  hyoid  muscles.  When  this  nerve 
is  cut  in  a  dog,  the  animal  can  no  longer  move  his  tongue, 
which  hangs  out  between  the  teeth ;  he  bites  the  tongue  when 
moving  the  jaws,  and  seems  to  feel  acute  pain  from  the 
wounds,  but  is  powerless  to  withdraw  the  tongue  behind  the 
dental  arches. 

2.  Spinal  Nerves.  —  The  thirty-one  pairs  of  nerves  given  off 
from  the  spinal  cord  fonn  mixed  roots,  and  contain  an  inex- 
tricable mixture  of  centripetal  and  centrifugal  nerves ;  how- 
ever, these  two  elements,  so  opposing  in  character,  are  for  a 
short  distance  separated,  and  called  by  the  name  of  the  spinal 
roots. 

The  anterior  roots  (Fig.  13,  A,  A,  A)  contain  centrifugal 
fibres,  that  is  to  say,  secretory  and  motor  nerves,  destined  as 
much  for  the  striated  as  for  the  smooth  muscles  (among 
others,  the  vaso-motor  apparatus). 


SPECIAL  PHYSIOLOGY. 


41 


The  posterior  roots  (Fig.  13,  P,  P,  P)  contain  centripetal 
or  sensory  fibres. 

This  exact  explanation  of  the  function  of  the  spinal  roots 
has  been  generally  attributed  to  Charles  Bell,  but  to-day  it 
is  admitted  that  the  glory  belongs  to  Magendie  (Vulpian). 
This  discovery  has  been  the  point  of  departure  in  all  our 
modern  conquests  in  the  physiology  of  the  nervous  system. 

Though  the  anterior  roots  possess  also  some  sensory  fibres, 
these  fibres  are  sent  off  to  them  from  the  posterior  roots. 
These  are  the  recurrent  fibres^  and  from  this  fact  has  arisen 
the  idea  of  recurrent  sensibility 
(Magendie,  CI.  Bernard) ;  in 
fact,  these  sensory  fibres  follow, 
in  their  progress  to  the  spinal 
cord,  the  anterior  roots  from 
centre  to  periphery,  and  then, 
either  at  the  anastomosis  of  the 
two  roots,  or,  more  probably,  at 
the  point  of  the  plexus  (cervi- 
cal, thoracic,  lumbar,  etc.),  they 
turn  back  towards  the  posterior 
roots,  entering  with  them  the 
medullary  centre.  The  recur- 
rent sensibility  of  the  anterior 
roots  is  then  no  exception  to 
the  general  rule ;  all  in  these  is 
centrifugal,  all  in  the  posterior 
roots  centripetal.  So,  when  an 
anterior  root  is  cut,  the  periph- 
eral end  only  is  still  sensible. 
This  experiment  is  a  most  com- 
plete demonstration  of  recur- 
rent sensibility,  especially  when 
we  observe  that  immediate  dis- 
appearance of  this  recurrent 
sensibility  in  the  anterior  root 
is  caused  by  section  of  the  pos- 
terior root. 

In  the  course  of  each  posterior  root,  a  little  before  the 


fn^ 


Fig.  13. 
Origin  of  the  spinal  roots.* 


*  The  anterior  surface  of  the  cord  is  here  shown.  A,  A,  A,  Anterior  spinal 
roots,  with  separate  origins,  uniting  afterwards  to  form  the  plexus  of  the  root. 
P»  P»  P.  Posterior  roots,  c,  d,  Anastomotic  tilaments  sometimes  found  between 
the  posterior  roots.  ,g,g,ff,  Ganglions  of  the  posterior  roots.  7n,m.  Mixed 
nerves,  formed  bv  the  union  of  two  roots. 


42 


NERVOUS  SYSTEM, 


point  of  junction  of  the  two  roots,  is  placed  a  small  ganglion. 
This  ganglion  is  made  up  of  a  collection  of  cells  having  the 
most  different  and  ill-defined  relations  with  the  nerve  tubes 
distributed  in  it.  We  do  not  know  the  functions  of  this 
ganglion ;  we  only  know  that  it  plays  some  part  in  nutrition 
{role  trophique)^  as  discovered  first  by  Waller,  and  since  con- 
firmed by  Bernard  and  many  other  physiologists.  When  an 
anterior  root  is  cut,  the  peripheral  or  distal  end  is  disorgan- 
ized, whilst  the  central  end  is  uninjured,  because  it  is  still 
connected  with  its  own  trophic  centre,  namely,  the  spinal 
cord.  On  the  other  hand,  when  a  posterior  root  is  cut  be- 
tween the  spinal  cord  and  the  ganglion,  the  end  remaining 
in  connection  with  the  ganglion  remains  intact,  whilst  the 


Fig.  14.  —  Changes  produced  in  the  nerves  by  section  of  the  spinal  root*.* 

end  fastened  to  the  spinal  cord  is  disorganized  (Fig.  14,  1 
and  3)  ;  the  ganglions  of  the  posterior  roots  possess,  then, 
the  property  of  trophic  centres  of  those  roots  connected  with 
them,  or,  in  other  words,  of  the  sensory  nerves.  Indeed,  there 
is  no  need  of  mentioning  that  if  the  mixed  nerve  (root  ?)  be 
cut  beyond  the  ganglion,  all  the  peripheral  or  distal  portion 
is  altered,  —  the  sensory  elements  as  well  as  the  motory  ele- 
ments (Fig.  14,  2). 

B.   Spinal  Cord. 

1.  Means  of  Conduction.  —  The  centripetal  nerves  return, 
then,  to  the  spinal  cord  by  the  posterior  spinal  roots ;  having 

*  Fig.  1.  The  section  is  made  in  the  posterior  root,  above  the  ganglion. 
The  portion  A,  comprising  that  between  the  section  and  th&  cord,  alone  under- 
goes any  change;  the  portion  A,  extending  to  the  ganglion  g,  remains  un- 
changed", as  well  as  the  anterior  root  S.  .     •,     v  i         u 

Fig.  2.  The  section  is  made  of  the  mixed  nerve,  immediately  below  the 
junction  of  the  two  roots.  The  portion  A  of  the  mixed  nerve  is  changed,  the 
two  roots  (the  posterior  S  and  its  ganglion  g)  remaining  unchanged. 

Fig.  3.  The  posterior  root  is  separated  from  the  cord  at  A.  Its  penpheraJ 
extremity  S  (turned  down)  undergoes  no  change.    (CI.  Bernard.') 


SPECIAL  PHYSIOLOGY.  48 

taken  more  or  less  part  in  the  formation  of  the  white  pos- 
terior columns,  they  then  join  the  gray  substance.  Thus  it  may 
be  said  that  sensibihty  traverses  the  posterior  roots,  the  pos- 
terior cohnnns,  and  tlie  gray  substance :  this  last  seems  more 
particularly  endowed  with  the  conduction  of  painful  se7isa- 
tions^  and  the  posterior  columns  to  the  sensations  of  touch  or 
contact.  In  fact,  by  experimentation  each  of  these  modes  of 
sensation  can  be  destroyed,  and  they  are  perfectly  isolated 
by  the  state  of  chloroformization  (or  etherization).  An  ani- 
mal whose  gray  axis  alone  has  been  bisected,  or  which  has 
been  subjected  to  the  action  of  chloroform,  loses  sensation  of 
pain,  but  yet  all  the  tactile  sensations  may  be  carried  to  the 
brain.  The  centrifugal  nerves  form  the  antero-lateral  columns, 
and  then  leave  the  spinal  cord  by  the  anterior  roots  of  the 
spinal  nerves ;  these  roots  start  fi-om  the  gi'ay  substance  of 
the  cord.  So  the  white  substance  of  the  cord  is  formed  by 
the  nerve  roots  that  go  through  this  spinal  cord  in  a  more  or 
less  oblique  direction,  and  also  by  vertical  fibres  (properly 
called  columns),  the  whole  enclosed  in  a  peculiar  uniting 
substance,  which  German  histologists  consider  to  be  the  em- 
bryonic form  of  the  connective  tissue.^ 

The  knowledge  of  the  centrifugal  functions  of  the  antero-. 
lateral  column  and  of  the  anterior  roots,  of  the  centripetal 
functions  of  the  posterior  roots  and  of  the  posterior  columns, 
form  the  essential  points  of  the  physiology  of  the  spinal  cord; 
but  in  order  to  satisfy  the  demands  of  pathology,  and  for  an 
explanation  of  the  numerous  facts  discovered  by  vivisections 
and  the  study  of  the  degenerations  of  the  fibres  of  the  spinal, 
physiology  should  seek  for  a  solution  of  the  following  ques- 
tions :  What  is  the  object  of  the  connective  tissue  in  the  struct- 
ure of  the  spinal  cord  ?  What  is  the  direction  of  the  fibres 
of  the  roots?  Do  these  go  directly  to  the  encephalon,  or  do 
they  terminate  in  the  cells  of  the  spinal  cord  ?  Are  the  fasci- 
culi of  the  cord  as  excitable  as  the  nerves?  Do  these  follow 
an  ascending  or  descending  course,  or  do  they  cross  from  one 
side  of  the  cord  to  the  other? 

Neuroglia,  a  kind  of  connective  tissue  in  the  spinal  cord, 
adopting  the  explanation  of  Virchow  (op.  cit.  pp.  71,  et  seq.) 
has  been  the  especial  study  of  anatomists  belonging  to  the 
school  at  Dorpat,  who,  moreover,  have  perhaps  slightly 
exaggerated  its  importance  (Owsjanikow,  Metzler,  Kupffer, 

^  Neuroglia,  or  nerve  cement.  Virchow's  "  Cellular  Pathology," 
.translated  by  Chance,  Am.  ed.,  p.  315. 


44  NERVOUS  SYSTEM. 

Bidder,  etc.).  They  consider  it  composed  of  a  connective 
mesh  work  (neuroglia)  formed  of  trabeculae  which  may  be  com- 
pared with  the  meshes  of  a  sponge,  and  in  certain  places  it 
may  even  be  condensed ;  as,  for  instance,  1st,  in  the  periphery 
where  it  forms  a  cortical  envelope ;  2d,  around  the  central 
canal  of  the  spinal  cord  (periependymal  nucleus)  (see  also, 
Yirchow,  op.  cit.  p.  312)  ;  3d,  upon  the  two  sides  which 
limit  the  posterior  median  fissure  (septum  posticum  of  Goll) ; 
4th,  around  the  posterior  horns,  where  it  forms  the  gelatinous 
substance  of  Rolando,  so  well  studied  by  Luys.^  The  essen- 
tial part  of  this  tissue  in  pathological  neoplasms  (new  for- 
mations) explains  the  importance  attached  to  its  study. 

With  regard  to  the  course  of  the  nerve  fibres  in  the  spinal 
cord,  we  have  already  insisted  in  this  connection  {vide  p.  34) 
that  the  spinal  cord  is  principally  a  commissure  between  the 
encephalon  and  the  peripheral  nerves,  and  indeed  vivisec- 
tions, and  especially  the  study  of  degenerations  in  the  spinnl 
cord  after  section  performed  experimentally,  or  after  patho- 
logical alterations,  have  proved :  1st,  that  the  posterior  roots 
are  almost  immediately  lost  sight  of  in  the  posterior  horns  of 
the  gray  substance,  some  by  their  horizontal  course,  others 
in  an  oblique  course  more  or.  less  upwards  or  even  down- 
wards; some  globules  of  the  posterior  horn  start  oiF  then 
from  fibres  which  mount  in  the  posterior  columns  even  to  the 
floor  of  the  fourth  ventricle,  and  perhaps  some  may  extend 
even  as  far  as  the  encephalon  (L.  Turck).  The  rest  of  the 
posterior  columns  is  formed  of  commissural  fibres  which 
unite  one  region  of  the  posterior  horns  to  another  of  those 
horns  situated  either  above  or  below.  2d.  The  anterior  roots 
start  from  the  anterior  horns»  and  traverse  almost  in  a  hori- 
zontal direction  the  white  antero-lateral  fasciculus ;  this  fas- 
ciculus is  formed  of  fibres  coming  from  the  corpus  striatum 
in  the  anterior  horns,  and  by  some  vertical  commissures  from 
one  portion  of  these  horns  to  another  situated  either  above  or 
below.     (Fig.  12.) 

The  excitability  of  these  fasciculi  of  the  spinal  cord  forms 
a  problem  difiicult  of  solution,  and  upon  which  physiologists 
are  far  from  agreement.  1st.  The  antero-lateral  column  is 
considered  inexcitable  by  most  physiologists ;  however,  Lon- 
get  has  often  obtained  movements  by  the  application  of 

1  J.  Luys.  *•  Recherches  sur  le  Syst^me  Nerve ux  Cerebro- 
spinal." Paris,  1865.  Luys  considers  that  this  substance  ia 
formed  of  nerve  elements,  and  not  of  connective  tissue. 


SPECIAL  PHYSIOLOGY.  45 

electricity  to  these  columns ;  more  recently  Fick  has  arrived 
at  similar  results,  and,  moreover,  has  found  that  these  columns 
respond  to  mechanical  irritations  (pinching  or  bruising).  We 
shall  conclude,  then,  as  has  this  last-named  experimenter, 
that  the  excitability  of  the  white  anterior  columns  is  real, 
though  less  intense  than  that  of  the  corresponding  roots; 
destined  to  transmit  the  commands  of  volition,  these  cerebro- 
spinal commissures  are  not  set  in  action  except  under  the 
influence  of  mechanical  agents  of  sufficient  energy.  2d.  All 
physiologists  from  the  time  of  Magendie  recognize  that  the 
posterior  columns  are  directly  excitable  by  irritants  more  or 
less  slight,  and  then  originate  painful  sensations.  Movements 
of  a  reflex  character  are  likewise  produced.  Sd.  Finally,  in 
order  no  longer  to  revert  to  these  facts  of  excitability,  let  us 
remark  that  the  gray  axis  of  the  spinal  cord  is  universally 
recognized  as  in  excitable. 

The  decussation  (crossing  over)  of  the  columns  of  the  spinal 
cord^  now  perhaps  admitted  as  a  general  fact,  has  been  for  a 
long  time  suspected  (Galen).  Experiment  has  shown  that 
this  decussation  occurs  in  the  difierent  columns  as  well  as 
in  different  parts  of  the  same  column  at  various  points: 
1st,  the  antero-lateral  column  is  but  little,  if  at  all,  the 
seat  of  decussation  throughout  the  length  of  the  spinal 
cord  properly  so  called  ;  this  decussation  occurs  at  the 
point  of  the  bulb  {decussation  of  the  pyramids),  but  in 
the  innermost  band  of  the  anterior  columns  there  is  none ; 
the  decussation  of  this  column  occurs  higher  up :  in  every  case 
there  is  found  in  front  of  the  protuberance  new  decussations 
of  fibres,  and  especially  nerve  fibres  that  go  from  the  brain 
to  the  roots  of  the  nerves  of  that  region  (facial,  motores 
oculorum)  ;  in  treatises  on  pathology  it  will  be  remarked  how 
a  knowlerdge  of  these  decussations  are  an  important  means  of 
explaining  paralyses  on  the  side  of  the  face  and  extremities  op- 
posite the  lesion  (Gubler).  2d.  According  to  the  majority  of 
physiologists,  the  posterior  columns  decussate  throughout  the 
length  of  the  spinal  cord,  in  such  wise  that  the  unilateral 
lesions  of  the  spinal  cord  destroy  sensibility  on  the  opposite 
side  and  motility  on  the  same  side  as  that  in  which  they 
occur.  3d.  Finally,  in  the  gray  substance,  which  also  serves 
its  a  conductor,  there  seems  to  be  a  decussation,  but  here  the 
facts  are  less  distinct ;  the  transmission  of  sensibility  appears 
in  every  way,  for  if  two  transverse  semi-sections  are  made  at 
different  heights  of  the  spinal  cord,  the  transmission  of  periph- 
eral (or  outward)  impressions  is  not  interrupted;  provided 


46  NERVOUS  SYSTEM. 

there  may  be  a  bridge,  however  small,  between  the  gray  sub- 
stance of  the  right  and  that  of  the  left,  peripheral  impression 
can  be  perceived,  and  thus  pain  be  caused  (indifferent  trans- 
mission, Stilling,  Vulpian). 

Brown-Sequard  has  even  gone  further  in  the  analysis  of 
special  conductors  composing  the  columns  of  the  spinal  cord ; 
according  to  him  there  are  more  numerous  and  even  more 
distinct  conductors  of  sensibility  than  have  been  generally 
supposed.  Basing  his  opinion  upon  clinical  observations  of 
anaBsthesia,  hyperaesthesia,  and  of  special  subjective  sensa- 
tions, he  allows  special  conductors  for  the  sense  of  touch, 
tickling,  temperature,  and  of  pain ;  all  these  conductors  are 
situated  in  the  posterior  columns  and  intercross  or  decussate 
in  such  a  manner  that  every  portion  of  the  conducting  zone 
in  a  posterior  lateral  half  of  the  spinal  cord  contains  conduc- 
tors coming  from  every  point  of  the  opposite  side.  Besides 
these  four  conductors  contained  in  the  posterior  columns, 
Brown-Sequard  notices  three  others  which  form  the  antero- 
lateral columns,  and  pursuing  a  direct  course  (at  least  in  the 
spinal  cord)  ;  these  are  the  conductors  of  voluntary  move- 
ments, vaso-motors,  and  conductors  of  the  muscular  sense  (!) ; 
these  constitute  a  sum-total  of  seven  special  conductors  com- 
prised in  the  spinal  cord. 

2.  The  Spinal  Cord  as  a  Nerve  Centre  ;  Reflex  Centres.  — 
Up  to  this  point  we  have  considered  the  spinal  cord  only  in  the 
light  of  a  conductor ;  but  we  have  mentioned  before  in  the 
general  study  of  nerve  centres  {vide  p.  32)  that,  judging  from 
modern  investigations,  the  spinal  cord  should  be  considered 
the  principal  one  of  these  centres.  The  globules  of  the  gray 
matter  of  the  spinal  cord  establish  in  a  more  or  less  direct 
manner  the  functional  connection  between  the  centripetal 
fibres  which  go  towards  this  centre,  and  the  centrifugal 
fibres  which  go  from  this  centre;  hence  they  preside  over 
the  reflex  actions. 

So  the  gray  matter  of  the  spinal  cord  suffices  for  the  trans- 
formation of  sensibility  into  movement,  and  most  often  it 
does  this  without  the  intervention  of  the  cerebral  function. 
If  a  section  of  the  spinal  cord  be  made  below  the  brain,  the 
peripheral  portions  by  this  interference  cease  from  being  in 
communication  with  a  reflecting  nerve  centre ;  and  yet  in 
such  an  instance  a  movement  of  the  extremities  may  be  pro- 
voked, as  for  example  by  tickling  the  bottoms  of  the  feet. 
This  same  fact  is  also  observed  in  certain  paralyses,  where,  in 
spite  of  alterations  of  the  upper  part  of  the  spinal  cord,  a 


SPECIAL  PHYSIOLOGY.  47 

shock,  cold,  tickling,  and  other  excitants  of  the  centripetal 
nerves,  will  produce  movements  as  well  as  secretions. 

Reflex  Movements.  —  The  spinal  cord  can  also  produce 
certain  very  complicated  reflex  movements  with  assistance 
of  the  brain  ;  of  this  kind  are  the  movements  of  defence  that 
are  observed  in  those  decapitated  animals  who  may  be  sub- 
jected to  irritations  (frogs  or  tritons).  Most  generally  the 
movements  of  progression  (walking,  leaping,  or  swimming) 
are  made  without  the  intervention  of  intellectual  action  ; 
volition  can  be  completely  unconcerned  in  the  process  of 
walking,  and  we  ordinarily  walk  without  knowing  it,  as  we 
might  say.  This  phenomenon  is  the  act  and  even  the  exclu- 
sive act  of  the  spinal  cord.  Tlie  brain  is  concerned  only  at 
certain  times,  when,  for  instance,  we  desire  to  regulate  the 
speed  either  by  retarding  or  hastening  our  step. 

From  the  moment  it  is  admitted  that  all  organic  acts  are 
the  result  of  a  peripheral  impression,  all  these  acts  have  a 
reflex  character ;  thus  all  organs  present  in  the  study  of  their 
functions  a  series  of  reflex  acts  in  which  we  shall  see  the 
spinal  cord,  acting,  not  as  auxiliary  to  the  brain,  but  as  a  true 
centre,  which  in  certain  cases  can  act  for  itself  alone.  A  few 
examples  of  reflex  acts  will  help  us  more  clearly  to  under- 
stand the  method  of  the  function  of  the  nerve  centres  and  of 
the  spinal  cord  in  particular. 

Sneezing  is  a  phenomenon  provoked  either  by  an  excita- 
tion brought  to  bear  on  the  nasal  mucous  membrane  or  by  a 
sudden  shock  of  the  sun's  rays  on  the  membranes  of  the  eye. 
This  peripheral  irritation  is  transmitted  by  the  trifacial  nerve 
to  the  Gasserian  ganglion,  whence  it  passes  by  a  commissure 
to  an  agglomeration  of  globules  in  the  medulla  oblongata  or 
in  the  protuberance  ;  from  this  point,  by  a  series  of  numerous 
reflex  and  complicated  acts,  it  is  transformed  by  the  media- 
tion of  the  spinal  cord  into  a  centrifugal  excitation  wliich 
radiates  outwards  by  means  of  the  spinal  nerves  to  the  expir- 
atory muscles. 

The  respiratory  movement  depends  on  the  spinal  cord. 
This  presides  over  the  regulai'ity  of  respiration ;  in  order  to 
set  up  this  reflex  phenomenon  the  sensitive  surfaces  of  the 
trachea  and  of  the  pulmonary  vesicles  (air  cells)  must  receive 
an  impression  from  the  introduction  of  external  air,  or  by  air 
vitiated  and  loaded  with  carbonic  acid  following  the  pul- 
monary gaseous  exchanges. 

The  movements  of  the  heart  are  the  result  of  analogous 
mechanism;  these  are  possible  only  when  the  internal  surface 


48  NERVOUS  SYSTEM. 

of  the  heart  is  in  direct  contact  with  the  blood.  Tliis  contact 
plays  the  part  of  a  peripheral  impression.  If  it  were  possible 
to  empty  the  heart  completely  of  all  the  blood  that  it  con- 
tained, it  would  stop  its  pulsations  until  a  few  drops  of  blood 
should  be  introduced,  after  which  its  movements  would  con- 
tinue; however  the  nerve  globules  that  preside  over  this 
reflex  act  are  situated  in  the  thick  walls  of  the  heart  (See 
circulation). 

Walking  is  also,  as  we  have  already  said,  a  reflex  phenom- 
enon ;  its  point  of  departure  is  the  peripheral  impression  pro- 
duced by  the  contact  of  the  foot  with  the  ground.  The  sole 
of  the  foot  is  plentifully  supplied  with  tactile  apparatus.  If 
this  peripheral  impression  be  but  imperfectly  transmitted  to 
the  nerve  centre,  reflex  action  has  no  longer  any  regularity. 
Thus  when  the  great  sciatic  nerve  has  been  compressed  in 
certain  postures,  during  the  few  moments  it  remains  para- 
lyzed (for  sensation  only)  walking  becomes  impossible  or  at 
least  painful. 

There  are  other  examples  of  reflex  action  fully  as  impor- 
tant as  the  preceding,  principal  among  which  are  the  secre- 
tions. It  is  generally  admitted  as  a  rule  that  previous  to 
every  secretion  a  peripheral  impression  is  transmitted  to  the 
nerve  centres  and  thence  to  the  gland.  The  salivary  secre- 
tion is  dependent'  on  the  centripetal  nerves  of  taste  which 
convey  the  impressions  of  taste  to  the  medulla  oblongata, 
whence  they  are  reflected  by  means  of  the  centrifugal  nerves 
(facial)  to  the  glands  and  their  vessels.  These  centrifugal 
nerves  seem  to  act  directly  on  the  cells  of  the  secretory  organ, 
independently  of  the  vascular  elements  ;  for  if  the  circulation 
in  a  gland  be  suppressed  simultaneously  with  the  excitation  of 
its  functions,  it  afibrds  to  the  surrounding  tissues  the  mate- 
rials no  longer  furnished  by  the  blood  and  the  gland  continues 
to  secrete.  The  secretion  of  gastric  juice  might  be  cited  as 
an  example  of  the  reflex  action  of  whose  existence  we  are 
unconscious;  but  in  this  connection  is  presented  the  peculiar 
fact,,  that  the  secretion  must  be  provoked  by  a  suitable  exci- 
tant, an  alimejit  (we  shall  mention  at  another  time  that  the 
introduction  of  foreign  bodies,  small  pebbles,  in  the  stomach 
provokes  no  secretion  of  true  gastric  juice,  but  of  a  mucus 
possessing  no  digestive  properties). 

"We  have  remarked  that,  in  the  eyes  of  the  physiologist, 
the  spinal  cord  extends  as  far  as  the  sella  turcica.  This  view 
is  sustained  by  the  study  of  reflex  actions  whose  centre  is  in 
the  cranial  portion  of  the  cord ;  there,  as  well  as  in  the  spinal 


SPECIAL  PHYSIOLOGY.  49 

portion,  we  find  masses  of  globules  serving  as  reflecting  cen- 
tres, transforming  the  sensory  impressions  into  motor  effects  ; 
moreover  these  centres  are  better  defined  and  their  irradia- 
tions more  localized  than  those  in  the  proper  spinal  cord. 

In  the  cephalic  region  there  are  found  a  series  of  centres 
beginning  low  down  and  going  upwards  (or  from  behind  for- 
wards), for  whose  exact  determination  modern  physiological 
investigations  are  especially  applied ;  we  shall  only  now  cite 
the  example  of  a  few  of  the  most  important,  as  these  centres 
will  be  more  exactly  pointed  out,  as  well  as  their  centripetal 
and  centrifugal  nerves,  when  the  different  functions  over  which 
they  preside  are  considered. 

In  the  bulb  is  found  :  the  centre  of  deglutition ;  —  of  the 
movements  of  mastication  ;  —  expression  of  imitation  ;  —  of 
speech  (olivary  bodies,  according  to  Schroeder  van  der  Kolk, 
and  Duchenne,  of  Boulogne:  consequently,  in  this  centre 
should  the  cause  of  those  singular  paralyses,  known  by  the 
name  of  labio-glosso-pharyngeal^  be  sought)  ;  —  the  centre  of 
respiratory  movements :  this  centre  is  composed  of  a  little 
mass  of  gray  substance  situated  towards  the  point  of  the  cala- 
mus scriptorius  (floor  of  the  fourth  ventricle),  this  is  the 
point  or  vital  knot  (Flourens,  Longet),  so-called  because  its 
lesion  causes  in  cold-blooded  animals  an  instantaneous  death, 
and  this  simply  by  an  immediate  arrest  of  respiration  (see 
respiration,  influence  of  oxygen  and  carbonic  acid  upon 
the  respiratory  centre)  ;  —  the  centre  of  cardiac  movements 
(moderating  fibres  of  the  pneumo  gastric)  ;  —  a  portion  of  the 
vaso-motor  centres  (Ludwig,  Thiry). 

At  the  protuberance,  and  as  high  up  as  the  cerebral  pedun- 
cules,  are  found :  another  portion  of  the  vaso-motor  centres 
(Tcheschichin) ;  —  the  centres  oi  innervation  of  the  movements 
of  locomotion:  these  last-named  centres  appear  to  be  in  com- 
munication with  the  different  encephalic  centres,  properly  so 
called,  which  are  attached  to  the  protuberance  by  peduncles 
(middle  cerebellar  peduncles  and  cerebral  peduncles).  Le- 
sions of  these  peduncles  occasion  a  disturbance  in  the  co- 
ordination of  movements ;  unilateral  lesions  give  rise  to  the 
peculiar  movements  of  rotation,  which  occur  under  the  form 
of  whirling  (a  continuous  motion  around  some  imaginary 
central  point),  or  of  motion  on  a  pivot  (the  posterior  portion 
of  the  animal  remains  fixed  whilst  the  anterior  portion  re- 
volves around  the  former  as  a  centre),  or  of  a  rolling  motion 
(rotation  around  the  longitudinal  axis  of  the  body),  or  of 
somersaults  (sudden  movements  forwards   or   backwards). 

4 


60  NERVOUS  SYSTEM. 

Finally,  the  protuberance  and  the  cerebral  peduncles  com- 
prise in  addition  motor-centres  for  the  movements  of  the  globe 
of  the  eye  (eyeball,  etc.). 

If  a  study  of  the  reflex  centres  situated  in  front  of  or  above 
the  before-named  centres  is  begun,  new  phenomena  compli- 
cate the  inquiry :  these  are  phenomena  of  perception^  or  of 
volition^  so-called,  which  will  be  studied  with  the  cerebral 
centres,  properly  so  called ;  but  even  at  the  level  of  the  pro- 
tuberance we  shall  have  to  admit  phenomena  oi perception^ 
and  we  shall  see  that  this  is  one  of  the  principal  seats  of  the 
reception  of  sensations,  but  not  of  their  conservation  under 
the  form  of  m,em,ory,  and  of  their  awakening  under  the  form 
of  ideas.  So  the  physiological  separation  between  the 
cephalic  portion  of  the  spinal  cord  and  the  cerebral  organs, 
strictly  speaking,  is  not  perfectly  distinct,  and  we  cannot  in 
fact  designate  the  protuberance  as  the  seat  of  transition,  as 
a  point  half-way  between  the  spinal  cord,  explanation  of 
whose  functions  is  relatively  so  easy,  and  the  brain,  which  pre- 
sents so  much  more  mysterious  phenomena. 

To  sum  up,  the  reflex  act  will  be  always  the  fundamental 
fact  in  the  functions  of  every  nerve  centre;  it  maybe  under- 
stood, then,  why  so  much  attention  is  paid  to  the  reflex  actions, 
their  classification,  the  discovery  of  influences  that  can  ex- 
aggerate or  diminish  them,  and  that  this  study  should  be 
principally  occupied  with  the  spinal  portion  of  the  cerebro- 
spinal axis  where  the  reflex  action  by  means  of  experimen 
tation  is  easily  isolated  from  all  phenomena  which  could 
complicate  it.  We  can  merely  pass  rapidly  in  review  over  the 
results  obtained  by  this  study,  which  commenced  only  at  the 
close  of  the  last  century. 

The  word  reflex,  or  reflection,  applied  to  certain  nervous 
phenomena,  was  first  used  by  Astruc  (1743),  who  sought  to 
explain  the  functions  of  the  brain,  and  particularly  the  motor- 
reactions  which  follow  a  sensory  impression,  by  a  sort  of 
reflection  of  the  latter  striking  against  the  columns  of  the 
brain  and  being  reflected  like  a  luminous  ray  from  a  polished 
surface.  The  comparison  was  well  made  to  illustrate  the 
method  of  study  of  the  reflex  phenomena,  but  applied  to  the 
brain  itself  could  lead  to  no  result,  for  in  the  latter  these  phe- 
nomena are  too  complicated.  It  was  only  by  following  the 
researches  of  Robert  Whytt,  Prochaska,  and  Legallois,  upon 
the  spinal  cord,  and  upon  that  which  is  called  the  se?isoriicm 
commune,  that  Prochaska  himself  was  able  to  distinctly  indi- 
cate both  the  principal  seat  (spinal  cord)  and  the  substance 


SPECIAL  PHYSIOLOGY,  51 

also  of  the  phenomena  which  then  took  the  name  of  reflex 
{impressionum  sensoriarum  in  motorias  reflexio)  (1784)  ; 
finally  the  histological  study  of  the  nerve  globule,  and  its  re- 
lations with  the  elementary  fibres,  aflfbrded  an  opportunity 
of  making  a  more  exact  account  of  the  mode  by  which  this 
reflection  is  made,  though  in  regard  to  this  latter  point  most 
of  the  facts  are  even  yet  quite  hypothetical.  Since  that  time 
Marshall  Hall,  Mueller,  Lallemand,  Flourens,  Longet,  CL 
Bernard,  etc.,  have  enriched  science  with  facts  numerous 
enough  to  allow  of  the  classification  of  the  reflex  actions,  of 
laying  down  the  precise  laws  of  their  production,  as  well  as 
the  influences  that  modify  them  (especially  in  regard  to  the 
medullary  reflex  actions). 

Classification  of  Reflex  Actions.  —  These  are  divided 
according  to  the  direction  followed  by  the  centripetal  and 
centrifugal  actions :  these  actions  present  two  directions ; 
either  the  nerves  of  the  cerebro-spinal  system,  which  have  occu- 
pied our  attention  up  to  this  point,  or  the  branches  of  the 
great  sympathetic,  which  will  terminate  our  study  of  the 
nervous  system. 

The  most  numerous  of  the  reflex  actions  follow  the  centrip- 
etal and  centrifugal  direction  of  the  spinal  nerve  filaments ; 
of  this  class,  the  larger  portion  we  have  already  cited  under 
deglutition,  sneezing,  cough,  walking,  etc.,  and  in  pathology 
a  large  number  of  morbid  reflex  actions,  as  vomiting,  tetanus, 
epilepsy,  etc. 

A  second  class,  almost  as  numerous,  comprises  those  reflex 
actions  where  the  centripetal  direction  is  in  the  course  a  sen- 
sory nerve  of  the  cerebro-spinal  system,  and  the  centrifugal 
direction  a  motor-nerve  of  the  great  sympathetic,  most  often 
a  vaso-motor  nerve ;  of  this  class  are  the  reflex  actions  which 
give  rise  to  most  of  the  secretions  (saliva,  gastric  juice,  etc.), 
to  the  phenomena  of  blushing,  or  pallor  of  the  skin,  to  erec- 
tion, to  certain  movements  of  the  iris,  to  certain  modifications 
in  the  pulsations  of  the  heart,  and  in  pathology  to  a  large 
number  of  phenomena  called  metastatic,  on  account  of  the 
great  difficulty  of  accounting  for  the  mechanism  of  their  pro- 
duction, as  for  instance  a  large  number  of  ophthalmias,  of  or- 
chitis, of  coryza,  which  depend  on  a  reflex  hyperaemia ;  and, 
on  the  other  hand,  dependent  on  a  reflex  anaemia,  as,  for  in- 
stance, certain  cases  of  amaurosis,  paralyses,  paraplegias,  etc.^ 

*  Vide  Ch.  Rouget,  Introduction  to  "  Diagnostic  et  Traite- 
ment  des  di verses  especes  de  Paralysies  des  Membres  Inferieurs.'* 
By  Brown- S^quard.     Paris,  1864. 


52  NERVOUS  SYSTEM. 

A  third  class  comprises  those  reflex  actions  whose  centrip- 
etal action  is  seated  in  the  nerves  of  the  sympathetic  (ob- 
tuse sensibility,  called  organic  in  the  viscera),  and  whose 
centrifugal  course  is  that  of  the  cerebro-spinal  motor  nerves 
(vital  relations)  ;  most  of  these  phenomena  belong  to  pathol- 
ogy ;  of  this  class  are  convulsions,  which  may  be  caused  by 
visceral  irritations  produced  by  intestinal  worms,  reflex 
eclampsia,  hysteria,  etc.;  as  a  normal  phenomenon  of  this 
kind,  the  respiratory  reflex  action  may  be  cited,  for  the  im- 
pression that  the  pulmonary  surface  sends  to  the  bulb  is 
transmitted  by  the  pneumo-gastric ;  which,  under  favorable 
circumstances,  is  brought  into  relation  with  the  nerves  of  the 
great  sympathetic,  or,  at  least,  forms  a  physiological  passage 
between  the  branches  of  the  great  sympathetic  and  those  of 
the  cerebro-spinal  system. 

Finally,  a  fourth  and  last  class  can  be  formed  of  reflex 
actions  whose  ways  of  centripetal  as  well  as  centrifugal  con- 
duction are  found  in  the  filaments  of  the  great  sympathetic ; 
we  shall  have  to  examine  at  another  time  whether  the  central 
action  for  this  class  is  located  in  the  masses  of  gray  matter  of 
the  cerebro-spinal  system,  or  in  those  of  the  ganglions  of  the 
sympathetic  chain  ;  of  this  class  are  the  obscure  reflex  actions 
and  those  which  preside  over  the  secretions  of  the  various 
intestinal  fluids  that  are  still  difficult  of  correct  analysis ;  also 
those  which  can  partially  explain  to  us  the  sympathies  that 
unite  the  various  phenomena  of  the  genital  functions,  espe- 
cially in  the  female  ;  also  the  dilatation  of  the  pupils  from  the 
presence  of  intestinal  worms  in  the  digestive  tract;  and  nu- 
merous reflex  pathological  actions  analogous  to  those  already 
spoken  of. 

Laws  of  JReflex  Actions.  —  When  a  sensory  impression 
causes  a  reflex  phenomenon,  the  production  of  this  latter  is 
subjected  in  its  intensity  and  anatomical  distribution  to  cer- 
tain precise  rules,  that  Ffluger  first  established  by  experimen- 
tation on  frogs  (laws  of  Pfluger),  and  that  Chauveau  has 
confirmed  by  his  experiments  on  the  great  mammalia.  Thus 
a 'feeble  irritation  produced  on  the  skin  of  the  hinder  extrem- 
ities (for  example,  on  the  right  side)  causes  a  reflex  movement 
in  the  muscles  of  the  same  extremity,  that  is  to  say,  in  the 
muscles  whose  motor  nerves  start  from  the  spinal  cord  of  the 
same  side  and  at  the  same  height  as  the  sensory  fibres  which 
have  been  excited  {law  of  unilaterality)  ;  if  the  excitation 
becomes  more  intense,  the  motory  reaction  is  manifested  on 
the  opposite  side,  in  the  corresponding  extremity :  that  is  to 


SPECIAL  PHYSIOLOGY.  63 

say,  by  means  of  the  symmetrical  nerves  (laio  of  symmetry)  ; 
and  this  corresponding  extremity  (left,  in  the  example  select- 
ed) presents  always  movements  less  intense  than  that  (right) 
which  received  the  excitation  (law  of  intensity).  Finally,  if 
the  excitation  still  increases,  the  motory  reaction  is  extended 
to  the  centrifugal  fibres  of  a  different  height,  but  always  ad- 
vancing towards  a  higher  (or  anterior)  portion  of  the  spinal 
cord,  that  is  to  say,  that  the  radiation  extends  from  below 
upwards,  from  the  spinal  cord  to  the  encephalic  cord  (bulb, 
protuberance,  etc.),  ilaw  of  radiation)  ;  lastly,  if  the  excita- 
tion and  consequently  the  motor-reaction  are  sufficiently 
energetic  to  be  propagated  fi'om  below  upwards  to  the  bulb 
and  protuberance,  the  reaction  becomes  general,  is  propagated 
in  every  direction,  both  downwards  and  upwards ;  in  such  a 
manner  that  all  the  muscles  of  the  body  take  part  in  it,  the 
bulb  acting  as  a  general  focus  whence  radiate  all  the  reflex 
movements  {Jaw  of  generalization). 

The  reflex  movements,  obeying  the  five  above-named  laws, 
present,  moreover,  the  remarkable  fact  that  they  are  pro- 
duced with  a  regularity,  a  co-ordination,  which  seems  to  indi- 
cate that  these  reflex  actions  are  adapted  to  a  certain  purpose 
or  aim ;  it  appears  as  if  there  w^ere  in  the  histological  disposi- 
tions of  the  spinal  cord  3. pre-established  mechaiiisrn^  the  mani- 
festations of  which  so  strongly  impressed  the  first  vivisectors, 
that  they  (Robert  Whytt,  Frochaska,  Legallois,  PflUger)  did 
not  hesitate  to  endow  the  spinal  cord  with  certain  psychical 
properties,  so  vague  and  ill-defined,  that  they  were  designated 
under  the  name  of  sensorium  commune^  volition,  perception, 
soul  (the  latter  must  not  be  confounded  with  the  ecclesiastical 
name  *'  soul"),  etc. 

Thus  a  frog  whose  brain  had  been  removed  (to  eliminate 
every  influence  foreign  to  the  spinal  cord),  reacted  when  the 
foot  was  pinched,  as  if  to  defend  himself;  if  the  skin  of  one 
of  his  extremities  was  cauterized  by  a  drop  of  acid  he  would 
wipe  it  off  with  his  foot,  if  perchance  the  acid  had  been  placed 
upon  the  bend  of  the  thigh  or  on  the  pelvic  integument;  more- 
over, if  the  leg  which  was  bent  thus  towards  the  thigh  were 
amputated,  the  animal,  reduced  to  his  medullary  centre,  was 
seen,  after  useless  and  droll  efforts  to  reach  the  injured  part 
{laio  of  unilaterality),  if  the  irritation  persisted  and  espe- 
cially if  it  increased,  to  use  the  limb  of  the  opposite  side  {law 
of  symmetry)  and  rub  or  wipe  the  part  irritated.  Should 
the  irritation  continue  he  would  execute  movements  with 
all  his  other  limbs,  a  forward  jump,  in  fact  a  flight.     Reflex 


54  NERVOUS  SYSTEM. 

movements  of  this  kind,  though  less  perfect,  are  performed 
by  man  during  sleep,  wlien  the  cerebral  organs  are  passive, 
and  when  the  fact  of  tickling  the  sole  of  the  foot  is  followed 
by  a  sudden  withdrawal  of  the  corresponding  leg,  or  of  both 
legs,  etc.  From  this  it  may  be  remarked  that  the  greatest 
number  of  reflex  actions  in  co-ordination  partake  of  the  nature 
of  defensive  movements. 

Yariations  in  ijitensity  of  the  Reflex  Actions.  —  Whatever 
may  be  the  phenomena  which  take  place  in  the  centres  of 
the  gray  matter  (nerve  globules)  at  the  time  of  the  produc- 
tion of  a  reflex  action,  it  is  distinguished  by  the  namfe  of 
refl.ex  power^  or  the  property  possessed  by  the  gray  axis  of 
the  spinal  cord  (or  similar  centres)  of  transforming  centripe- 
tal impressions  into  centrifugal  reactions ;  this  expression 
seems  to  present  a  certain  convenience  of  language,  for  it 
relates  to  agents  that  appear  to  convey  their  action  upon  the 
reflex  power^  either  to  diminish  or  increase  this,  without  in 
any  way  acting  upon  the  centripetal  or  centrifugal  portion 
of  the  act,  but  solely  upon  the  central  act.  We  can  here  call 
to  mind  numerous  investigations,  by  means  of  which  the 
central  action  of  these  agents  can  in  this  way  be  precisely 
fixed,  and  we  can  distinguish  among  them  analogous  agents 
which  convey  their  action  upon  the  peripheral  paths;  a  rec- 
ollection of  the  beautiful  experiments  of  Claude  Bernard  with 
woorara  {curare)  on  the  motor  nerves  {vide  physiology  of  the 
muscles,  muscular  irritability).  In  connection  with  the 
agents  that  modify  reflex  power  we  will  cite  as  examples :  — 

The  surrounding  temperature :  reflex  actions  are  more 
energetic  and  easier  to  provoke  in  summer  than  in  winter 
(Brown-S^quard,  Cayrade),  but  yet  reflex  power  is  rapidly 
exhausted  during  wann  weather ;  —  sections  of  the  spinal  cord 
or  its  separation  from  the  encephalon:  in  these  cases  the 
reflex  actions  are  exaggerated,  which  seems  to  be  due  to  an 
irritation  of  the  centres  even  from  the  act  of  the  section, 
rather  than  to  the  interruption  of  all  communication  between 
these  centres  and  other  centres  called  moderators  (Setsche- 
now) ;  and  indeed  this  exaggeration  of  the  reflex  power  after 
sections  lasts  but  a  short  time ;  —  a  certain  number  of  poisons 
convey  their  action  directly  upon  the  centres  and  exaggerate 
the  reflex  power ;  among  these  are  strychnine,  morphine, 
picrotoxine,  nicotine,  veratrine,  cicutine,  and  certain  patho- 
logical products  of  the  organism,  as  in  the  septic  infections 
(septicemia),  uremia,  severe  icterus. 

On  the  other  hand,  reflex  power  is  diminished  by  anaBmia, 


SPECIAL  PHYSIOLOGY.  55 

by  numerous  successive  irritations  which  weaken  it,  and  by 
certain  toxical  or  medicinal  agents  as  hydrocyanic  (prussic) 
acid,  bromide  of  potassium,  atropine,  etc. 

C.  Encephalon. 

General  Functions  of  the  cerebral  or  encephalic  Centres 
properly  so  called.  —  By  generalizing  the  expression  reflex 
phenomena  we  can  apply  it  to  the  phenomena  which  occur 
between  the  spinal  cord  and  encephalon ;  in  fact,  the  brain 
does  not  appear  to  communicate  directly  with  any  portion  of 
the  periphery,  and  can  only  perceive  that  which  goes  on  in 
the  spinal  cord ;  thus  in  the  brain  infinite  reflex  actions  occur 
between  the  numerous  centres  that  are  united  by  numerous 
commissures  ;  and,  in  those  phenomena  which  are  considered 
voluntary ^  the  brain  reacts  upon  the  spinal  cord  and  thence 
outwards,  in  accordance  with  that  series  of  actions  which 
constitute  the  perception  or  ego. 

Sensations.  —  The  brain  is  then  the  seat  of  the  interior 
phenomenon  of  perception,  under  the  influence  of  an  exter- 
nal agent  whose  action  is  transmitted  to  it  by  means  of  the 
peripheral  nerves  and  by  the  spinal  cord.  Indeed  perception 
is  not  produced  during  sleep,  at  which  time  the  brain  is  at 
rest :  but  in  speaking  of  the  brain  we  should  include,  in  the 
view  of  sensations,  the  whole  encephalic  mass  and  not  merely 
its  superficial  layers,  as  a  large  number  of  acts  attributed  to 
perception  seem  to  take  place  at  the  protuberance  (see 
before,  p.  50)  ;  so  also  a  portion  of  the  hemispheres  and  cere- 
bellum can  be  removed  without  thereby  causing  the  loss 
of  sensation. 

llie  phenomena  of  perception  are  divided  into  those  which 
give  us  precise  information  of  external  objects,  such  as  spe- 
cial sensations,  which  we  shall  refer  to  under  tlie  head  of 
organs  of  special  sense ;  and  those  called  general  sensations, 
which  warn  us  only  of  those  modifications  that  our  organs 
undergo,  without  giving  us  precise  information  of  the  nature 
of  the  agents  producing  these  modifications  ;  pain  is  the  spe- 
cial type  of  this  latter  kind  of  sensations.  Intermediate  be- 
tween these  two  kinds  of  sensations  have  been  placed  those 
called  subjective  and  objective. 

The  general  or  subjective  sensations  can  also  present  two 
phases  :  in  the  first,  the  sensation  (pain,  for  instance)  is  per- 
fectly localized,  as  the  sensation  of  a  burn  upon  the  skin  ; 
in  the  second  form,  on  the  contrary,  the  sensation  is  vague 
and  difl[icult  to  localize ;  as  the  general  malaise  that  marks  the 


56  NERVOUS  SYSTEM. 

commencement  of  asphyxia.  Some  have  endeavored  to  ex- 
press this  difference  by  applying  to  the  latter  form  of  sensa- 
tion the  name  oi  sentiment^  and  reserving  for  the  former  that 
of  sensatio7i  properly  speaking.  But  a  similar  influence  may 
give  rise  at  the  same  time  to  a  general  localized  sensation  and 
a  vague  sensation  or  sentiment.  Thus  it  is  that  hunger  is 
manifested  by  a  sensation  that  we  localize  at  the  epigastrium 
(stomach),  and  also  by  a  vague  and  indefinite  sentiment  that 
is  experienced  throughout  the  organism  and  which  spreads  to 
the  extremities  in  the  form  of  fatigue.  The  same  is  true 
concerning  thirst,  which  sensation  is  referred  to  the  throat  and 
also  to  a  general  sentiment  of  languor. 

The  general  non-localized  sensations  are  a  very  interesting 
study  for  the  physician  ;  one  of  the  most  curious  of  these  in 
the  light  of  its  pathological  modifications  is  the  sentiment  of 
our  existence ;  this  sensation  passes  ordinarily  unnoticed, 
because  it  is  habitual  and  constant ;  it  is  pretty  much  the 
same  as  with  the  miller  who  does  not  notice  the  noise  of  his 
mill.  When  this  sensation  is  noticed  it  indicates  usually  a 
pathological  condition  whose  seat  is  most  generally  in  the 
cerebro-spinal  centre  (hyperaesthesia),  and  makes  us  expe- 
rience to  a  painful  degree  all  the  phenomena  going  on  in  our 
organism ;  this  feeling  of  habitual  malaise  constitutes  hypo- 
chondria. 

Localized  sensations  are  ordinarily  produced  under  the 
influence  of  an  external  action  on  some  definite  portion  of 
the  surface  of  the  body,  and  are  conveyed  to  the  nerve-cen- 
tres by  means  of  nerves  which  are  always  definitely  deter- 
mined. But  should  some  cause  act  upon  these  nerves  in  any 
portion  of  their  extent,  we  perceive  the  sensation  which  occurs, 
just  as  if  the  action  were  brought  to  bear  upon  the  point 
where  these  nerves  originate.  If,  for  instance,  the  ulnar  nerve 
is  suddenly  compressed  at  the  posterior  portion  of  the  elbow 
on  its  inner  aspect  (epitrochleo-olecranon  groove,  or  groove 
near  the  inner  condyle  of  the  humerus),  we  localize  the  pain- 
ful impression  so  caused  at  the  cutaneous  extremity  of  this 
nerve,  or,  in  other  words,  at  the  inside  of  the  hand  (and  espe- 
cially in  the  little  finger).  This  phenomenon  constitutes  what 
is  called  the  eccentricity  of  the  sensations  /  whatever  may 
be  the  point  where  the  nerve  is  attacked,  the  sensation  inva- 
riably is  eccentric ;  even  when  the  central  portion  is  attacked 
we  localize  the  sensation  at  the  peripheral  end  of  the  sensitive 
nerve  in  question.  Patients  struck  down  by  cerebral  apoplexy 
comjilain  of  peripheral  pains  whose  cause  is  wholly  central. 


SPECIAL  PHYSIOLOGY.  57 

These  considerations  afford  the  clew  of  the  mechanism  by 
which  hallucinations  are  prodaced,  whose  cause  is  located  in 
the  encephalon  and  gives  rise  to  certain  sensations  attributed 
by  the  patient  to  the  periphery. 

This  explains  also  the  associated  sensations ;  an  external 
sensation  arriving  at  a  nerve-centre  can  there  produce  an 
excitation  sufficient  to  radiate  towards  the  neighboring  cen- 
tres ;  these  will  then  give  us  sensations  identical  with  those 
we  should  have  experienced  had  the  excitation  been  produced 
on  those  nerves  that  make  communication  between  these  cen- 
tres and  the  periphery.  In  this  way  a  foreign  body  introduced 
into  the  ear  may  produce  as  an  associated  sensation  a  feeling 
of  tickling  in  the  back  part  of  the  throat,  and  perhaps  even 
coughing  and  vomiting.  These  associations  are  caused  on 
account  of  the  nearness  of  the  central  gray  nucleus  of  the 
trifacial  and  of  the  nucleus  of  the  glosso-pharyngeal  and 
pneumogastric,  from  which  excitations  perceived  by  the 
former  radiate  towards  the  latter. 

There  are  examples  of  associated  sensations  still  more  start- 
ling that  seem  due  to  the  same  mechanism :  in  certain  per- 
sons an  irritation  on  the  foot  between  the  third  and  fourth 
toe  produces  a  sensation  of  tickling  in  the  sub-umbilical 
region  of  the  abdomen;  an  irritation  on  the  skin  of  the 
scrotum  will  give  rise  to  pains  in  the  right  hypochondriac 
region,  etc. 

Memory  and  Volition.  —  Finally,  the  sensations  present  in 
addnion  to  the  preceding  this  peculiar  fact,  that  they  can  be 
stoied  up  in  the  cerebral  organs;  the  impressions  are  fixed 
there  to  reappear  at  a  later  time  ;  in  this  way  are  caused  those 
phenomena  designated  under  the  name  of  memory.  The 
sensations  thus  reserved  in  a  latent  condition  reappear  by  a 
mechanism  analogous  to  that  of  the  associated  sensations,  and 
this  revival  of  a  sensation  can  bring  on  a  number  of  others 
similar  or  analogous :  as,  one  idea  calling  up  another,  and 
what  is  called  association  of  ideas.^ 

^  llie  cell  in  the  spinal  cord  is  also  susceptible  of  preserving  up 
to  a  certain  point  the  impression  which  has  been  produced  by  a 
centripetal  nerve,  though  generally  the  former  retains  nothing  after 
having  brought  its  peculiar  reflex  action.  Thus  a  certain  habit  of 
reflex  actions  is  brought  about,  which  terminates  in  happening 
more  readily  and  regularly.  In  fact,  the  spinal  cord  can  be  edu- 
cated; we  need  only  cite  the  example  of  persons  who  play  upon 
musical  instruments,  who  finally  attain  the  faculty  of  executing  a 
musical  piece  or  tune  almost  without  any  conscious  volition,  and 


68  NERVOUS  SYSTEM. 

However,  physiology  goes  no  iixrther;  it  has  but  little 
means  of  knowing  what  is  the  internal  and  intimate  nature 
of  the  mechanism  of  the  seat  of  thoughts  or  ideas ;  as,  for 
example,  we  know  that  softening  of  the  brain,  characterized 
sometimes  by  gay  and  sometimes  by  sad  thoughts,  has  its 
seat  in  the  gray  cortical  substance ;  little  doubt  can  thus  be 
had  that  the  seat  of  thought  is  in  a  general  way  located  in 
this  substance ;  as,  moreover,  a  large  number  of  vivisections 
would  seem  to  prove. 

The  central  phenomenon  of  volition  is  equally  beyond  our 
study,  at  least  when  it  forms  no  part  of  association  of  ideas. 
Still,  we  know  at  least  that  injuries  in  the  brain  destroy  those 
manifestations  called  voluntary,  and  paralyze  the  voluntary 
movements  of  the  opposite  side ;  viz.,  movements  of  the  right 
side  of  the  body  are  abolished  by  a  lesion  having  its  seat  in 
the  left  hemisphere  of  the  brain,  and  vice  versa.  The  centrif- 
ugal conducting  nerves  of  volition  decussate  on  leaving  the 
brain.  However,  this  decussation  must  not  be  localized  only 
at  the  lower  extremity  of  the  pyramids ;  it  extends  through- 
out a  larger  space  from  this  point,  to  the  most  anterior  portion 
of  the  protuberance.  A  lesion  which  may  be  seated  in  any 
part  of  this  extent  may  then  affect  at  the  same  time  fibres 
which  have  already  crossed  (decussated)  and  those  which 
have  not ;  thus  there  may  ensue  those  peculiar  alternating 
paralyses,  which  for  example  may  be  located  in  the  right  side 
of  the  face  and  on  the  left  side  of  the  remainder  of  the  body 
(see  physiology  of  the  spinal  cord,  pp.  43  and  45). 

We  find  equally  in  the  case  of  phenomena  of  motility  as  in 
the  volitional  j^henomena  associations  analogous  to  those 
which  we  have  explained  in  regard  to  sensation  or  sensi- 
bility. Thus  a  centre  becoming  the  seat  of  a  lively  action 
can  do  so  to  such  a  degree  that  its  activity  may  extend  even 
to  the  neighboring  centres. 

This  is  the  mechanism  of  all  the  little  convulsive  move- 
ments and  also  of  involuntary  associated  movements.  This 
also  explains  why  it  is  that  during  a  very  intense  and  general 
muscular  exertion,  as  for  instance  when  lifting  a  heavy  weight, 
a  person  involuntarily  contracts  the  frontal  muscles ;  as,  also 
when  sneezing,  the  eyes  are  involuntarily  closed,  etc. 

Thus  we  might  as  a  general  rule  state  that  all  our  volun- 
tary movements  are  associated  move7n£7its,  hecsmse  we  cannot 

without  the  intervention  of  the  brain.     The  cerebral  memory  is 
simply  in  a  higher  degree  a  sort  of  medullary  memory. 


SPECIAL  PHYSIOLOGY,  59 

contract  one  muscle  apart  from  others,  but  contraction  of 
muscles  usually  occurs  in  groups ;  this  association  is  wholly 
performed  in  the  spinal  cord  by  certain  groupings  of  globules 
and  fibres,  and  the  brain  serves  only  to  excite  this  group  of 
globules ;  this  association  is  found  in  those  movements  which 
are  purely  of  a  reflex  character,  as  those  of  defence  which 
are  observed  in  experiments  on  decapitated  animals  (physi- 
ology of  the  spinal-cord,  p.  53). 

Special  functions  of  certain  cerebral  centres^  or  what  is 
called  encephalic  centres. 

We  shall  not  enter  into  the  detail  of  the  numerous  hypo- 
theses which,  even  in  the  experimental  investigations  of  the 
modern  school,  have  founded  the  physiology  of  the  encepha- 
lic organs.  The  system  founded  upon  the  union  of  spec- 
ified faculties  of  the  mind  to  particular  circumscribed 
portions  of  the  brain  is  regarded  as  an  illusion  {Phrenology^ 
system  of  Gall),  especially  when  an  attempt  is  made  to  de- 
fine these  faculties,  otherwise  arbitrarily  classified,  according 
to  the  development  of  certain  external  portions  of  the  skull 
(Craniology). 

However,  very  recently  it  has  been  believed  according  to 
certain  pathological  observations  that  the  centre  of  faculty 
oi  language  or  at  least  the  memory  for  words  is  seated  in  the 
third  convolution  of  the  left  (Broca)  or  right  (Bouillaud) 
hemisphere.  It  is  evident  that  perception  and  thought  form 
an  undefined  phenomenon,  which  depends  upon  a  peculiar 
activity  of  the  cerebral  cells  and  of  an  association  of  these 
cells  connected  by  numerous  commissures;  yet  our  knowl- 
edge is  too  uncertain  to  localize  these  functions. 

The  tubercula  quadrigemina  {corpora  quadrigemina)  are 
the  centre  of  visual  perceptions,  and  of  reflex  movements 
which  cause  the  dilatation  or  contraction  of  the  iris  (Herbert, 
Mayo,  and  Flourens)  ;  yet  when  the  cerebral  hemisplieres 
are  removed,  luminous  impressions,  though  perfectly  per- 
ceived (the  animal  follows  with  his  eyes  and  head  the  move- 
ments of  a  lighted  taper),  are  not  preserved  and  cannot  give 
rise  to  an  intellectual  effort ;  in  this  aspect  of  the  case  the 
sensation  must  be  imperfect,  — the  animal  looks  but  does  not 
see.  The  tubercular  quadrigemina  are  to  visual  sensations 
what  the  protuberance  generally  is  to  sensations  of  touch, 
pain,  etc. 

It  is  probable  that  these  tubercles,  moreover,  preside  over 
Other  functions,  not  now  known,  since  they  appeal'  considera- 
bly developed  in  animals  completely  depiived  of  the  power 


60  NERVOUS  SYSTEM. 

of  sight  (Talpa  Asiatica,  some  of  the  Ophidio-Batrachians, 
Myxine) ;  Serres  also  considered  these  as  centres  for  co-ordi- 
nation of  movements ;  the  explanation  of  this  seems  to  be 
in  the  fact  that  these  tubercles  have  some  relation  to  excito- 
motory  impulsions,  which  would  authorize  their  classification 
with  the  cerebral  centres,  as  a  medium  between  the  protu- 
berance and  the  clusters  of  cerebral  and  cerebellar  cells  (see 
p.  33,  fig.  12). 

The  functions  of  the  cerebellum  are  a  problem  difficult  of 
solution ;  experimentation  and  observation  from  pathological 
conditions  give  us  but  negative  and  contradictory  results ; 
ablation  of  the  cerebellum  shows  that  this  large  portion  of  the 
encephalon  takes  no  part  in  the  intellectual  functions,  strictly 
speaking,  nor  in  the  manifestations  of  sensation,  memory, 
instinct,  or  volition.  Its  peculiar  functions  are  so  difficult  to 
define  that  almost  all  possible  opinions  have  been  proposed. 
Leaving  out  of  consideration  the  opinion  of  Willis,  who,  at 
the  time  when  the  theory  of  the  animal  spirits  held  sway, 
made  it  the  point  of  departure  for  the  innervation  of  organic 
functions^  we  notice  that  some  physiologists  (Lapeyronie, 
Pourfour  du  Petit,  Duges),  basing  their  opinion  upon  the 
apparent  continuity  of  the  inferior  cerebellar  peduncles  with 
the  posterior  columns  of  the  spinal  cord  (conductors  of  sen- 
sation or  sensibility),  considered  the  cerebellum  as  the  central 
organ  of  sensibility,  the  sensorium  commune  to  which  all  the 
peripheral  sensations  pass  for  elaboration  and  arrangement, 
especially  including  the  auditory  (Foville)  and  visual  sensa- 
tions (Lussana).  We  have  already  noticed  that  this  role  of 
the  centre  of  sensation  belongs  in  part  to  the  protuberance 
and  in  part  to  the  tubercula  quadrigemina.  With  less  rea- 
son, but  perhaps  more  fortunate  in  his  hypothesis,  Gall  con- 
sidered the  cerebellum  as  a  centre  of  animal  love,  or  erotic 
passion  ;  indeed,  in  spite  of  the  experiments  and  contradic- 
tory observations  by  Leuret,  Segalas,  Combette,  and  Vulpian, 
we  notice  several  reasons  brought  out  by  experimentation 
and  clinical  observation  by  Budge,  Valentin,  Wagner,  Lus- 
sana, which  would  seem  to  give  some  appearance  of  reality 
to  the  hypothesis  of  Gall,  and  to  assign  an  important  func- 
tion to  the  middle  lobe  in  the  manifestations  of  genital  in- 
stinct. 

The  cerebellum,  however,  seems  to  have  an  important  part 
in  the  apparatus  for  the  co-ordination  of  movements  as  ap- 
pears from  the  experiments  of  Rolando,  and  especially  from 
the  more  recent  and  numerous  experiments  of  Flourensj  in  the 


SPECIAL  PHYSIOLOGY.  61 

animals  (birds)  from  which  this  latter  physiologist  removed 
the  cerebellum,  "flying  sensations  and  perceptions  remained  ; 
the  possibility  of  executing  combined  movements  likewise 
persisted,  but  the  co-ordination  of  movements  into  movements 
of  regulated  and  definite  locomotion  was  lost."  This  has  been 
the  view  adopted  by  the  majority  of  physiologists ;  and  Lus- 
sana  has  even  gone  further,  and  attributes  to  the  cerebellum 
the  function  of  the  centre  of  muscular  sensibility.  However, 
these  functions  of  locomotion  are  manifested  only  when  the 
deeper  portions  of  the  cerebellum  are  injured,  whilst  super- 
ficial injuries  do  not  give  any  result,  and  leave  us  without 
any  indications  of  the  functions  of  the  cortical  layers  of  the 
cerebellum.  Moreover  Vulpian  and  Philippeaux  have  caused 
no  disturbance  of  locomotion  in  fishes  after  ablation  of  the 
cerebellum  ;  let  us  recall  to  mind  also  that  physiology  of  the 
«pinal  cord  has  furnished  almost  all  the  elements  necessary  to 
explain  the  reflex  mechanism  of  locomotion ;  moreover,  Kiiss 
saw  a  rabbit  whose  head  he  had  amputated  with  dull  scissors, 
thereby  hacking  the  head  so  as  to  prevent  hemorrhage,  jump 
from  the  table  and  run  the  whole  length  of  the  room  with  a 
perfectly  defined  movement  of  locomotion,  and  we  shall 
arrive  at  the  conclusion  that,  in  spite  of  the  very  numerous 
solutions  that  have  been  offered  to  explain  the  physiology  of 
the  cerebellum,  we  still  possess  no  precise  notion  of  the  func- 
tions of  this  nervous  centre. 

The  corpora  striata  and  optic  thalami  are  inexcitable,  as 
well  as  the  gray  axis  of  the  spinal  cord,  and  all  the  gray 
centres ;  we  cannot  then  arrive  at  a  knowledge  of  their  func- 
tions except  by  their  destruction  in  animals,  or  by  the  study 
of  the  clinical  phenomena  which  follow  their  alteration,  either 
by  the  presence  of  a  tumor  or  by  a  hemorrhage.  In  these 
cases  no  lesions  of  general  sensibility  have  been  proved,  nor 
of  any  special  sensibility,  and  we  must  admit  that  the  optic 
thalamic  in  spite  of  their  name,  have  no  more  concern  with 
vision  than  the  corpora  striata  have  with  the  sense  of  olfac- 
tion. Lesions  of  these  centres  produce  only  paralyses  (par- 
alysis on  the  opposite  side,  as  we  have  seen  a  propos  to  the 
conductors  in  the  spinal  cord),  and  we  may  consider  the  cor- 
pora striata  and  optic  thalami  as  grand  excito-motory  centres, 
but  without  assigning  to  the  former  the  movements  of  the 
posterior  extremities,  and  to  the  latter  those  of  the  anterior 
extremities. 

The  corpus  callosum  (trabs  cerebri),  and  the  different  com- 
missures between  the  cerebral  hemispheres  taught  in  anatomy, 


62  NERVOUS  SYSTEM. 

are  by  no  means  the  seat  of  the  soul,  as  held  by  certain  au- 
thorities; these  are  only  bridges  of  white  substance  that 
harmonize  the  functions  of  the  two  hemispheres  which  they 
connect ;  but  here,  moreover,  we  must  not  attach  a  meaning 
to  words  nor  pretend  to  a  decision  not  supported  by  the  facts ; 
as,  for  instance,  is  done  by  Treviranus,  who  asserts  that  the 
corpus  callosum  furnishes  the  brain  with  the  faculty  of  com- 
parisons, as  if  comparison  were  made  between  the  thoughts 
which  come  from  the  left  and  right,  and  not  between  impres- 
sions, or  successive  thoughts  (Duges). 

The  cerebral  hemispJieres,  and  especially  their  gray  cortical 
substance,  are  the  most  essential  portion  of  the  brain.  Here 
are  accomplished  the  elaborations  of  the  sensations  in  the 
form  of  thoughts.  The  experiments  of  Flourens,  from  which 
Longet  especially  has  drawn  legitimate  conclusions,  prove 
that  animals  from  which  the  hemispheres  have  been  removed,- 
as  we  have  before  remarked  in  connection  with  the  protuber- 
ance and  tubercula  quadrigemina,  continue  to  feel,  hear,  see, 
and  receive  the  impressions  of  taste ;  but  that  these  impressions 
do  not  remain  nor  awake  any' response,  nor  seem  to  produce 
any  associations  of  ideas ;  they  do  not  look  nor  hear,  nor 
smell,  nor  taste ;  in  short,  the  cerebral  lobes  "  are  the  recep- 
tacle where  all  sensations  take  a  distinct  form,  and  produce 
a  continued  remembrance."  There  may  be  a  perfect  sensa- 
tion without  the  cerebral  lobes ;  but  this  sensation  bears  a 
resemblance  to  that  eflfect  which  is  noticed  in  a  person  wrapt 
in  profound  meditation,  and  receiving  an  external  irritation 
(as,  for  instance,  when  a  fly  lights  upon  the  hand),  but  whose 
meditation  is  not  in  any  way  interrupted,  and  who  does  not 
appear  to  notice  the  irritation  (Vulpian,  Taine). 

On  the  other  hand,  the  cerebral  lobes  preside  over  spon- 
taneous movements.  An  attentive  analysis  of  the  movements 
of  a  frog  or  of  a  fish  deprived  of  the  cerebral  lobes  proves 
that  these  creatures  swim  only  under  the  influence  of  reflex 
actions  perfectly  co-ordinated,  which  the  impression  of  the 
water  in  contact  with  their  integument  may  provoke ;  they 
progress  as  if  impelled  by  a  pre-established  mechanism,  as  il 
subjected  to  a  reaction  which  makes  their  progress  an  imperi- 
ous necessity,  until  a  new  impression,  as  for  instance  coming 
in  contact  with  the  borders  of  the  vessel  or  basin,  causes  the 
frog  to  assume  a  state  of  immobility  and  normal  posture,  a 
necessity  no  less  imperious  than  the  first.  There  are  not 
seen  in  the  behavior  of  the  animal  any  of  those  capricious 
changes,  or  spontaneous  movements  from  repose  to  activity 


SPECIAL  PHYSIOLOGY.  63 

and  vice  verf^d^  that  characterize  animals  with  uninjured  cere- 
bral lobes,  and  who  hence  are  capable  ofvoliti07i  or  intentional 
spontaneity. 

The  faculties  called  intelligence  and  instinct  unite  these 
opposing  phenomena,  perception  and  thought  on  the  one 
hand,  volition  and  spontaneous  moveme^its  on  the  other. 
The  seat  of  the  phenomena  which  we  have  just  analyzed  is 
localized  in  the  cerebral  hemispheres,  especially  in  the  gray 
cortical  substance  of  these  hemispheres.  An  animal  deprived 
of  these  hemispheres  is  plunged  in  a  peculiar  sleep,  dreamless 
sleep  (Flourens).  On  the  contrary,  pathological  conditions 
which  over-excite  the  cerebral  convolutions  awaken  in  them 
chains  of  disordered  thoughts,  which  a  diseased  brain  considers 
external  realities ;  of  this  order  are  the  delirium  in  meningitis, 
madness  in  its  acute  and  chronic  varieties ;  thus  those  who 
are  concerned  in  the  care  and  study  of  insanity  seek  to  attach 
to  these  organs  the  alterations  of  intelligence,  especially  the 
somatic  element,  in  which  psychical  disturbances  are  simply 
the  manifestation  of  the  disease. 

The  development  of  the  cerebral  convolutions,  and,  perhaps 
we  might  even  say,  the  quality  of  the  gray  cortical  substance, 
are  in  proportion  to  the  amount  of  intelligence  possessed  by 
the  animal ;  idiots  seem  to  have  fewer  nerve  globules  than 
persons  of  sound  intellect.  In  the  autopsy  of  idiots  portions 
of  the  brain  are  found  made  up  of  connective  tissue,  and 
containing  a  large  amount  of  embryonic  globules  which  have 
not  been  transformed  into  nerve  elements.^ 

D.   Great  Sympathetic. 

The  great  sympathetic  is  composed  of  a  series  of  ganglions 
arranged  along  the  side  of  the  vertebral  column  (Fig.  15),  at 
the  side  of  each  vertebra  (except  in  the  cervical  region,  where 
there  are  groups  of  three  great  ganglions).  The  ganglions 
of  the  same  side  are  connected  by  commissures,  whence  re- 
sult cords  arranged  in  chaplets. 

Moreover,  these  globular  groups  send  commissures  from 
one  portion  towards  the  spinal  cord  {rami  commwiicantes), 
and  from  another  portion  towards  the  viscera  and  other 
organs  in  general  (nerves  of  the  great  sympathetic).  At  a 
certain  distance  from  the  chain  of  the  great  sympathetic,  in 
the  course  of  those  commissures,  going  either  towards  the 

*  Kiiss  in  P.  Ad.  Rousseau.  These  de  Strasbourg,  1866.  (Note 
"  Sur  le  Role  et  I'lmportance  du  Globule  en  Physiologie.) 


64 


NERVOUS  SYSTEM. 


spinal  cord  or  the  viscera,  new  ganglionic  masses  are  found. 
Of  this  class  numerous  globular  clusters  are  arranged  like 
the  rounds  of  a  ladder  on  the  nerves  that  return  to  the  vis- 
cera. The  most  remarkable  of  these  groups  are  the  semilunar 


Pig.  15.  —  Direction  and  general  distribution  of  the  great  sympathetic  nerve. 
(Dalton,  "  Human  Physiology.") 

ganglion,  called  by  Bichat  the  abdominal  brain.  Finally,  at 
a  more  distant  portion  in  the  path  of  the  visceral  nerves  a 
new  series  of  ganglions  are  distributed  in  the  walls  oi  the 
organs,  being  ordinarily  only  of  microscopical  dimensions. 


SPECIAL  PHYSIOLOGY,  65 

Some  of  these  occur  in  tlie  tissue  of  the  intestinal  walls,  in 
the  muscular  structure  of  the  heart,  in  the  bronchi,  etc. 
(visceral  or  parenchymatous  ganglions). 

By  means  of  these  numerous  ganglions  or  clusters  of  nerve 
globules,  the  sympathetic  system  seems  to  serve  as  a  centre 
of  certain  reflex  actions,  as  it  possesses  fibres  having  centrif- 
ugal, and  others  having  centripetal,  properties.  The  great 
sympathetic  has  been  considered  the  seat  of  all  those  nerve 
phenomena  more  or  less  mysterious  that  have  been  embel- 
lished with  the  name  of  sympathetic,  and  which  we  now  call 
reflex  phenomena.  It  must,  however,  be  remembered  that 
the  great  sympathetic  is  in  no  wise  a  system  by  itself;  it 
simply  shares  in  the  properties  and  functions  of  the  medullary 
system,  and  is  associated  with  the  latter. 

In  fact,  its  nerve  fibres  and  filaments  are  excitable  to  the 
same  agents  as  the  spinal  nerves,  that  is,  to  electricity  and 
chemical  agents ;  but  the  physiological  excitant  that  we  have 
previously  designated  by  the  name  of  volition  or  will  has  no 
effect  upon  this  system ;  consequently,  the  movements  which 
are  produced  in  the  department  of  the  great  sympathetic  are 
all  involuntary.  On  the  other  hand,  those  movements  re- 
sulting from  the  artificial  excitation  of  the  nerve  require  a 
definite  amount  of  time  for  their  production.  They  are 
manifested  slowly  and  cease  slowly.  This  new  difference 
has  the  same  relation  to  the  peculiar  nature  of  the  nervous 
and  sympathetic  fibres  as  in  the  case  of  the  fibres  of  Remak 
(pp.  25  and  26),  and  of  the  muscles  to  which  they  are 
distributed  {smooth  muscles ;  see  farther  on).  The  exci- 
tation of  the  filaments  of  the  great  sympathetic  gives  also 
origin  to  the  phenomena  of  sensibility,  but  an  intense  as  well 
as  long-continued  irritation  must  be  brought  to  bear  upon 
them.  In  the  pathological  conditions  the  great  sympathetic 
is  much  more  excitable,  and  becomes  both  the  seat  and  con- 
d  uctor  of  a  large  number  of  painful  sensations.  Formerly,  too, 
the  independence  of  this  nervous  system  in  its  relations  to 
the  cerebro-spinal  system  was  much  exaggerated.  It  was 
made  to  preside  as  a  central  organ  over  the  functions  of  the 
viscera  in  general,  and  more  especially  of  those  belonging  to 
nutrition.  Experiments  by  CI.  Bernard  demonstrate  that  the 
sub-maxillary  ganglion  may  serve  as  a  centre  for  the  salivary 
secretion ;  yet  this  result  has  lately  been  denied  by  Schiff.  \ 

'  Mau.  Schiff,  *'  Lecons  sur  la  Physiologie  de  la  Digestion," 
Vol.  I.,12thLe9on. 

6 


66  NERVOUS  SYSTEM. 

The  ganglions  that  occur  in  the  wall  of  the  viscera  at  the 
terminal  branches  of  roots  from  the  great  sympathetic  serve 
as  a  centre  for  partial  movements  of  the  visceral  muscles, 
and  regulate,  by  way  of  illustration,  the  peristaltic  contrac- 
tions of  the  intestinal  walls.  Other  ganglions  (of  Wrisberg, 
semi-lunar,  of  the  hypogastric  plexus,  etc.)  might  be  con- 
sidered as  provisionary  centres  where  the  nervous  action 
coming  from  a  higher  point  can  be  accumulated.  The  ma- 
jority of  the  phenomena  of  the  visceral  functions  have  as 
their  nervous  centre  the  spinal  cord,  and  even  in  the  vaso- 
motor functions  (see  circulation)  the  sympathetic  has  only  a 
power  of  impression  derived  from  the  superior  portion  of  the 
spinal  axis.  The  same  may  be  said  in  reference  to  its  influ- 
ence on  the  heart,  and  most  of  the  visceral  reflex  actions 
whose  centre  is  found  in  the  spinal  cord ;  so  that  the  expres- 
sion "great  sympathetic  system"  has  at  this  present  time 
but  little  physiological  signification. 


PAUT   THIRD. 

CONTRACTILE   ELEMENTS.  — MUSCLE  AND    ITS 
ADJUNCTS. 

I.  Muscles  in  General. 


The  muscular  elements  are  produced  by  metamorphosis  of 
the  globules  of  the  embryo.  By  studying  their  formation  we 
may  best  understand  the  three  types  presented  by  the  muscu- 
lar system,  —  the  contractile  cell^  smooth  fibre^  and  striated 
fibre.  We  notice,  at  the  same  time, 
that  the  property  of  changing  their 
shape  (or  contractility)^  which  is  char- 
acteristic of  these  different  kinds  of 
muscles,  is  only  the  sjtme  property, 
carried  to  a  higher  degree,  which  we 
have  ascertained  belongs  to  globules 
in  general. 

When  an  embryonic  globule  is 
slightly  lengthened,  and  its  nucleus 
becomes  more  visible,  etc.,  we  have 
the  contractile  cell  (Fig.  16,  ^),  as  it  is 
found,  for  instance,  in  the  smaller  ar- 
teries. 

When  the  cells  are  imited  at  the 
ends  in  such  a  way  as  to  form  a  vari- 
cose fibre,  with  elongated  nuclei  in 
different  parts,  and  granular  contents, 
we  have  the  smooth  fibre,  in  which,  Y\g  le 
moreover,  are  found  all  the  elements 
of  the  cell  (Fig.  16,  ^). 

Finally,  as  the  fibre  straightens,  and  the  fusion  of  the  cells 
becomes  complete,  we  have  the  striated  fibre  (Fig.  16,  *),  the 

*  1,  Contractile  cell.    2,  Smooth  muscle.    3,  Striped  muscle. 


Di.agram  of  the  three 
forms  of  the  contractile  or 
muscular  element  * 


68 


CONTRACTILE  ELEMENTS. 


envelopes  of  the  primitive  cells  being  represented  by  the 
covering  of  the  fibre,  or  sarcolemma ;  the  cellular  nuclei  by 
corpuscles,  placed  at  intervals  upon  the  inner  surface  of  this 

covering;  and  the  cellular  con- 
tents by  the  granular  contents 
of  the  fibre:  the  latter  appear 
to  be  formed  from  a  liquid  por- 
tion, and  from  granulations  {sar- 
cous  elements  of  W.  Bowman) 
which,  being  grouped  in  series, 
either  perpendicular,  or  parallel 
with  the  axis  of  the  fibre,  give 
us  muscles  with  longitudinal  or 
transverse  striae,  the  latter  form 
being  the  most  common  (Fig.  17, 
a  and  b).  It  is  not  unlikely  that 
other  effects  are  due  to  the  artifi- 

Pig.  17.— Different  appearances  of   cial  mode  of  preparation. 

p     musce.  rpi^^  striated  muscle  has  been 

the  most  minutely  examined,  and  we  will,  therefore,  begin 
our  study  of  the  muscles  with  this  form. 


II.   Striated  Muscle. 

These  muscles  appear  as  clusters  of  fibres,  remarkable  on 
account  of  their  transverse  striation.  Histological  analysis 
shows  this  fibre  not  to  be  the  simple  element  which  it  ap- 
pears ;  it  is  itself  composed  of  longitudinal  ^fibrils,  exhibiting 
small  nodosities  arranged  in  clusters,  one  above  the  other ; 
the  regular  arrangement  of  the  nodosities  of  the  adjacent 
fibrils  in  transverse  series  produces  the  striated  aspect  of  the 
fibre  as  a  whole.  (SeeFig.  17,a,  5,  c,  c?).  Opinions  differ  as  to 
the  nature  of  these  nodosities.  According  to  Ch.  Robin,  they 
are  caused  simply  by  the  appearance  of  points  which  are 
alternately  light  and  dark,  and  are  themselves  caused  by  a 
difference  in  refraction  in  the  different  parts  of  the  fibril ; 
while  Rouget  supposes  them  to  be  produced  by  the  spiral 
twisting  of  the  fibrillary  filament,  forming  a  helix,  the  coils 
of  which  are  more  or  less  closely  brought  together  accord- 


*  a,  Nonnal  appearance  of  a  recent  primitive  fasciculus,  with  its  transverse 
striae,  b,  Fasciculus  treated  by  dilute  acetic  acid  (the  nuclei  showing  more  dis- 
tinctly the  nucleoli),  c,  Under  the  action  of  concentrated  acetic  acid  me  contents 
escape  at  the  extremity  of  the  envelope  (sarcolemma).  d,  Fatty  atrophy. 
(Virchow,  "Pathologic  Cellulaire.") 


STRIATED  MUSCLE. 


69 


ing  to  the  condition  of  the  muscle.  We  shall  consider 
this  explanation  again  when  analyzing  the  ultimate  action 
that  constitutes  what  is  called  the  contraction  of  the 
muscle. 

The  principal  feature  in  the  study  of  the  muscle  is  that  it 
changes  its  shape,  and  appears  under  two  different  forms; 
thus  a  fusiform  muscle,  meeting  with  no  opposition,  becomes 
globular  under  certain  circumstances.  The  former  condition 
is  usually  called  the  state  of  repose,  and  the  latter  the  state 
of  action.  In  order  not  to  anticipate,  we  will  call  tlie  first 
simply  form  No.  1;  the  second,  form  No.  2  (Fig.  18). 


Fig.  18. —The  muscle,  under  forms  No.  1  and  No.  2.* 

We  will,  then,  proceed  to  examine  the  properties  and  phe- 
nomena exhibited  by  the  muscle  under  form  No.  1;  and, 
afterwards,  those  under  form  No.  2.  As  the  muscle  origi- 
nates from  the  globules,  and  still  represents,  in  its  structure, 
the  elements  of  which  they  are  chiefly  composed,  we  shall  find 
both  in  it,  and  in  the  two  forms  which  it  takes,  the  principal 
physiological  properties  of  the  globule ;  viz.,  elasticity,  chem- 
ical phenomena,  electro-motor  power,  etc. 

These  properties  being  known,  we  shall  speak  more  at 
large  of  those  which  are  chiefly  made  use  of  in  the  animal 

*  SH,  Articulation  of  the  shoulder  joint.  CH,  Articulation  of  the  elbow. 
H,  Humerus.  B,  Biceps  in  the  state  of  repose  (form  No.  1).  W,  Biceps  assum- 
ing the  form  No.  2,  in  consequence  of  section  of  its  tendon.  (The  tendon  of 
the  biceps  is  actually  inserted  into  the  radius,  but  since,  during  flexion,  the  lat- 
ter becomes  a  fixed  body  with  the  ulna,  the  fore-arm  is  represented  in  the  dia- 
gram by  a  latter  bone,  in  which  the  biceps  appears  to  be  inserted.) 


70  CONTRACTILE  ELEMENTS. 

economy,  especially  the  faculty  of  passing  from  the  first  to 
the  second  form  ;  and,  in  seeking  for  the  reason  of  this  phe- 
nomenon, we  shall  study,  in  the  muscle,  as  we  have  already 
done  in  regard  to  the  cells  in  general,  that  most  essential 
property  of  all  living  elements,  excitability  or  irritability. 

A.  The  Muscle^  under  Form  JVb.  1. 

Elasticity.  —  One  of  the  most  remarkable  properties  of  the 
muscle  is  its  elasticity.^ 

By  elasticity  we  mean  that  property  of  bodies  by  which 
they  are  diverted  from  their  primitive  form,  and  return  to  it 
as  soon  as  the  extending  cause  ceases  to  act.  Different  bodies 
present  great  differences  in  this  respect,  and  the  elastic  prop- 
erties vary,  according  to  w^hether  the  change  is  made  with 
more  or  less  facility,  and  the  return  to  the  original  form  is 
more  or  less  complete.  We  say  that  the  elasticity  is  perfect 
when  this  return  is  perfect  (an  ivory  ball,  for  instance) ;  that 
it  is  imperfect  when  the  return  is  not  complete  (example,  a 
lump  of  dough)  ;  that  the  elasticity  is  great  when  the  change 
is  made  with  difficulty,  and  the  return  is  sudden  (as  with  a 
steel  blade),  and  that  it  is  slight  when  the  change  is  easy, 
and  there  is  slight  tendency  to  return  to  the  original  form 
(example,  a  willow  twig). 

The  muscle,  under  form  No.  1,  may  be  said  to  be  slightly 
and  perfectly  elastic.  In  this  example  muscles  are  flabby, 
and  may  be  easily  stretched,  so  that  the  arm,  deprived  of  its 
muscular  envelope  (directly  after  death),  is  no  more  readily 
moved  than  when  the  muscleg  were  in  place;  this  proves 
that  in  this  state  the  muscles  readily  distend  {slight  elasticity)^ 
and  afterwards  assume  their  original  conditio7i  {perfect  elas- 
ticity). In  the  same  way,  the  muscular  bags  (auricles,  ven- 
tricles, stomach)  are  so  easily  distended  by  any  thing  which 
has  a  tendency  to  dilate  their  cavities,  that  their  elasticity 
can  be  compared  only  to  that  of  a  soap-bubble. 

This  slight  and  perfect  elasticity  is  not  ?i  purely  physical 
property  of  the  muscle ;  for  it  depends  on  the  life  and  nutri- 
tion, or  at  least  on  the  chemical  composition,  of  the  muscle, 
and  this  composition  is  directly  under  the  influence  of  the 
life  of  this  element  (circulation  and  innervation).  When 
the  muscles  have  remained  long  in  a  state  of  inactivity,  and 
are,  consequently,  ill-nourished,  they  lose  a  portion  of  their 

^  See  Hitter.  *'  Des  Propriet^s  Physi(jues  du  Muscle."  Th^se 
de  concours.     Strasbourg,  1863. 


STRIATED  MUSCLE.  71 

elasticity,  —  witness  the  pain  and  difficulty  experienced  in 
extending  the  forearm,  after  it  has  been  long  kept  in  a 
sling. 

The  muscles  of  a  corpse  are  at  first  flabby  and  extensible, 
preserving  any  shape  which  may  be  given  them ;  still  they 
are  slightly,  but  imperfectly,  elastic ;  later,  they  enter  the 
state  known  as  that  of  cadaveric  {corpse-like)  rigidity^  when 
immense  force  is  required  to  stretch  them  out,  and,  being  once 
stretched,  they  can  no  longer  regain  their  original  form,  and 
thus  become  strongly  and  imperfectly  elastic.  This  cadaveric 
rigidity  was  formerly  attributed  to  coagulation  of  the  fibrin  of 
the  blood  (J.  Muller)  ;  but  it  is  now  generally  supposed  to  be 
owing  to  the  coagulation  of  the  myosin,  or  of  its  derivative, 
the  syntonin  (KUhne),  an  albuminoid  substance,  which  coag- 
ulates spontaneously,  and  closely  resembles  the  fibrin  of  the 
blood.  The  muscular  fluid  coagulates  by  heat;  thus  the 
cadaveric  rigidity  of  a  muscle  may  be  produced  instantane- 
ously, by  immersing  it  in  a  fluid  at  a  temperature  of  45^  c. 
(See  farther  on,  p.  82.) 

We  see,  thus,  that  slight  and  perfect  elasticity  is,  up  to  a 
certain  point,  characteristic  of  the  life  of  the  muscle ;  and 
that  it  differs  entirely,  in  this  respect,  from  the  elasticity  of 
the  ligaments,  of  the  bones,  and,  above  all,  of  the  elastic 
tissue;  since  their  elasticity  remaining  always  the  same, 
depends  only  on  the  mechanical  arrangement  of  the  fibres  of 
which  these  tissues  are  composed,  and  is  thus  purely  physi- 
cal. This  cannot  be  said  of  the  elasticity  of  the  muscle; 
neither  can  we  look  upon  it  as  an  essentially  vital  property, 
for  it  appears  to  depend  principally  upon  the  chemical  com- 
position of  the  muscle.  In  fact,  by  injecting  hot  water  (ex- 
periment of  Brown-Sequard),  or  defibrinated  blood,  or  serum, 
or  even  any  simple  alkaline  liquid,  into  the  arteries  of  an 
animal  lately  killed,  it  may  be  for  a  time  preserved  from  this 
rigidity,  which  is  brought  on  by  the  acidity  of  the  muscle, 
and  is  opposed  by  its  alkalinity.  If,  for  instance,  the  arm 
being  in  repose,  and  the  tendon  of  the  biceps  cut,  we  find 
that  it  immediately  shrinks  a  little ;  and,  having  been  pre- 
viously slightly  extended,  assumes  its  natural  form  only  by 
the  natural  distance  of  its  points  of  insertion,  and,  conse- 
quently, exerts  upon  these  latter  only  slight  traction.  This 
is  called  the  tonicity  of  the  muscles;  but  we  see  that  it  is  not 
a  special  property  of  the  muscle,  but  is  only  the  result  of  its 
elasticity,  brought  into  play  by  its  insertions,  the  distance  of 
which  prevents  it  from  perfectly  assuming  its  proper  form; 


72  CONTRACTILE  ELEMENTS. 

tonicity  is  only  its  tendency  to  assume  tliat  form.  Neither 
is  the  so-called  tonicity  of  the  sphincters  a  property  inde- 
pendent of  their  elasticity.  These  muscles,  under  their 
natural  form,  No.  1,  are  arranged  in  order  to  completely 
close  the  openings  which  they  circumscribe,  so  that  these 
openings  really  do  not  exist,  and  are  only  formed  when 
dilated  by  a  body  animated  by  a  certain  force,  which  brings 
into  play  the  elasticity  of  the  sphincters  (tonicity  of  authors). 
Tliis  tonicity  or  perfect  elasticity  of  living  muscle  is  under 
the  dependence  of  the  nervous  system.  When  the  nerves 
that  belong  to  these  muscles  are  cut,  the  tonicity  disappears, 
the  muscles  become  flaccid,  and  the  sphincters  are  relaxed.* 
The  origin  of  tonicity  is  not  yet  demonstrated.  It  has  a 
reflex  character.  Brondgeest  has  shown  that  if  the  sensory 
nerves,  coming  from  a  part  where  the  muscles  are  in  a  per- 
fect condition  of  tonicity^  be  cut,  this  tonicity  will  immedi- 
ately disappear  {vide  p.  108). 

These  considerations  concerning  the  elasticity  and  the  nat- 
ural form^  No.  1,  of  the  muscle,  help  us  to  solve  a  question 
which  is  differently  answered  by  other  writers:  Are  the  flex- 
ors of  the  extremities  superior  in  force  to  the  extensors,  or 
vice  versa?  From  the  fact  that  in  repose,  or  after  death,  the 
limbs  are  generally  found  to  be  in  a  state  of  semi-flexion, 
it  has  been  supposed  that  there  is  a  predominance  of  force 
on  the  part  of  the  flexors ;  but  where  there  is  repose  there 
is  no  struggle,  and  without  a  struggle  there  can  be  no  pre- 
dominance of  force.  This  position  only  proves  that  the 
flexors  are  shorter  than  the  extensors,  and  that  extension, 
under  these  conditions,  brings  into  play  the  elasticity  of 
the  flexors.  But  suppose  the  state  of  repose  to  cease,  and 
the  struggle  begin,  as,  for  instance,  in  tetanus,  when  all  the 
muscles  are  contracted,  and  we  shall  find  all  the  extremities, 
and  the  trunk  itself,  extended;  whence  we  conclude,  con- 
trary to  the  majority  of  writers,  that  the  extensors  are  more 
powerful  than  their  antagonists. 

Chemical  Phenomena. — The  muscle,  in  its  natural  form,  No. 
1,  lives  and  receives  nourishment,  that  is  to  say,  its  chemical 
composition  is  constantly  changing :  it  also  breathes ;  a  muscle, 
even  though  detached  from  the  body,  as  long  as  it  lives  con- 
tinues to  absorb  oxygen,  and  give  out  carbonic  acid ;  and  the 
longer  it  can  breathe,  the  longer  it  lives,  as,  for  instance,  when 

*  See  CI.  Bernard.  *'  Propri^t^  des  Tissus  Vivants.'*  When 
the  nerve  of  a  mnscle  is  cut,  the  venous  blood  which  flows  from  the 
muscle  closely  resembles  arterial  blood. 


STRIATED  MUSCLE.  73 

placed  in  an  atmosphere  containing  oxygen.*  In  the  living 
animal,  the  venous  blood  which  flows  from  the  muscle  differs 
essentially  from  the  arterial  blood  which  enters  it,  having 
less  oxygen,  and  more  carbonic  acid. 

The  respiration  of  a  muscle  is  in  direct  proportion  to  its 
life,  and  as  the  latter  depends  in  a  great  measure  on  the 
trophic  (nutrient)  influence  of  the  nervous  centres,  if  the 
nerve  of  a  muscle  be  cut,  the  gaseous  exchange  will  be  con- 
siderably les^,  as  well  as  the  elasticity  be  diminished  (see 
preceding  page).  We  explained  the  simultaneous  modi- 
fication in  the  chemical  phenomena  and  the  elasticity  of  the 
muscle,  by  saying  that  its  respiration  is  accelerated  by  its 
tonicity  ;  the  meaning  of  which  word  we  have  already  given. 

It  should  be  added  that  the  muscle,  under  form  No.  1,  is 
alkaline ;  under  this  form,  no  doubt,  its  chemical  phenomena^ 
are  not  sufficient  to  produce  acids  capable  of  neutralizing  tho 
alkalinity  of  the  blood  contained  in  the  muscle. 

Electro-motor  Power. — The  muscle  possesses  electro-motor 
properties,  that  is  to  say,  it  gives  rise  to  electric  currents ; 
this  may  be  proved  by  making  the  two  wires  of  a  galvanom- 
eter communicate,  one  with  the  interior 
part  of  a  Tnuscle,  or  transverse  section, 
the  other  with  the  outside  of  the  same 
muscle,  or  longitudinal  section  ;  the 
current  flows  always  from  the  surface 
to  the  centre ;  that  is,  the  surface,  or 
longitudinal  section,  is  positive  in  re- 
lation to  the  centre,  or  transverse  sec- 
tion (Fig.  19). 

Presuming  that  this    electro-motor       ..      fig.  i9. 

.Pi.       .  ,        ,        ,  ,       , ,  Muscular  current.* 

power  might  lurnisn   the  key  to  the 

principal   properties   of  the   muscle,  especially  to  that  by 

which  it  passes  from  form  No.  1  to  that  of  No.  2  (for  we 

*  Hermann  (Berlin,  1867)  maintains  that  the  phenomena  of 
gaseous  exchange  presented  by  the  muscles,  when  separated  from 
the  body,  and  brought  into  contact  with  the  air,  are  phenomena  of 
si-mple  putrefaction.  But  Paul  Bert  has  shown  them  to  be  really 
phenomena  of  respiration,  of  life,  and  has  proved  the  existence  of 
these  respiratory  exchanges,  though  in  a  less  degree,  in  different 
tissues.  See  "  Lecons  sur  la  Physiologie  compai^e  de  la  Respira- 
tion. ' '     1870.     4e  Legon ;  —  "  Respiration  des  TissiAs. ' ' 

*  In  the  galvanoscopic  circuit  the  current  flows  from  a  to  ft,  as  indicated  by 
the  arrows,  a,  Longitudinal  surface  of  the  muscle,  positive  (-!-)•  ^i  Section  or 
transverse  surface  negative  ( — ). 


74  CONTRACTILE  ELEMENTS. 

find  that,  in  this  case,  the  current  is  reversed  or  disappears) 
much  study  has  been  given  to  this  subject;  and,  after  speci- 
fying the  conditions  of  the  current,  it  has  been  sought  to 
exphiin  them  by  what  is  called  the  theory  of  peripolar-eleo 
tric  molecules.  We  will  not,  however,  explain  in  detail  this 
theory,  for  it  is  probable  that  the  study  of  these  currents  is  not 
of  supreme  importance  in  the  physiology  of  the  muscle,  but 
that  they  should  be  considered  simply  as  the  result  of  the 
chemical  phenomena  of  which  the  muscles  are  the  seat,  and 
which  are  more  or  less  active  as  the  layers  may  be  more  or  less 
superficial.  In  fact,  the  shape  of  the  pieces  of  muscle  em- 
ployed in  experiments  has  great  effect  upon  the  direction  of 
the  current ;  a  muscle  may  possess  its  normal  electric  cur- 
rent, and  yet  have  lost  all  its  other  properties ;  thus,  poisons 
which  kill  the  muscle  have  not  always  the  same  effect  upon 
its  electro-motor  power;  finally,  similar  currents  have  been 
observed  in  living  tissue  of  various  kinds,  even  in  vegetables, 
as,  for  instance,  in  pieces  of  the  pulp  of  a  potato. 

B.    The  muscle^  under  form  No.  2. 

The  muscle,  in  this  state,  only  differs  essentially  in  a  change 
of  form  from  what  it  was  in  the  preceding  state :  it' is  shorter 
and  thicker ;  a  fusiform  muscle  becomes  globular.  The  dif- 
ference may,  in  general,  be  estimated  at  f ,  that  is,  the  muscle 
under  form  No.  2,  becomes  shorter  by  f  of  its  former  length 
under  form  No.  1.  But  its  transverse  dimensions  increase  in 
exact  proportion  to  the  diminution  of  its  longitudinal  dimen- 
sions, and  there  is,  consequently,  no  change  in  its  bulk.  If 
we  place  in  a  graduated  vessel,  full  of  water,  a  muscle  of 
form  No.  1,  and  by  any  excitation  cause  it  to  pass  into  form 
No,  2,  we  shall  find  no  change  in  the  level  of  the  fluid. 
Lately,  however,  Valentin  has  ascertained,  by  an  extremely 
minute  process,  that  a  muscle,  in  passing  from  the  first  to  the 
second  form,  increases  in  density  in  the  ratio  of  t^oi7»  ^^^ 
this  fraction  represents  such  a  slight  diminution  of  bulk  that 
it  seems  quite  unworthy  of  notice. 

The  bulk  remaining  the  same,  we  have  then,  in  order  to 
make  a  comparative  study  of  the  muscles,  under  form  No.  2, 
only  to  consider  it  in  the  triple  aspect  of  the  properties 
already  studied  in  form  No.  1 :  its  elasticity,  chemical  phenom- 
ena, and  electro-motor  power. 

JElasticity.  —  The  muscle  in  form  No.  2,  when  not  pre- 
vented from  completely  taking  this  form,  is  as  soft  and  elastic 
as  in  form  No.  1.     If  it  is  then  handled,  it  is  found  to  be  ex- 


STRIATED  MUSCLE.  75 

tremely  soft.  This  is  a  phenomenon  occasionally  observed 
by  surgeons  in  an  amputated  limb,  especially  the  thigh ;  the 
muscles  which  have  been  cut  are  seized  with  tetanuSj  con- 
tract, and  pass  into  form  No.  2.  Nothing  hinders  their 
taking  this  form  completely,  as  they  have  no  longer  any 
lower  insertions,  and  they  withdraw  towards  the  root  of  the 
limb,  and  here  form  a  soft,  fluctuating,  and  globular  mass, 
which  has  been  compared  to  a  collection  of  liquid.  It  even 
appears,  and  it  is  true,  that  the  muscle  is  softer  under  form 
No.  2  than  under  form  No.  1.  If  we  attempt  to  reduce  the 
muscle  from  the  second  foi-m,  we  find  that  it  allows  itself  to 
be  extended  easily,  and,  after  having  been  drawn  out,  returns 
perfectly  to  the  shape  from  which  it  was  diverted,  and  is 
thus,  exactly  as  in  form  No.  1,  slightly  and  perfectly  elastic. 
Besides  being  softer,  its  elasticity  is  slighter  under  form 
No.  2,  that  is,  it  is  more  easily  diverted  from  this  form  than 
from  form  No.  1 :  this  is  shown  by  two  of  Weber's  experi- 
ments. 

1.  This  physiologist  constructed,  out  of  muscular  fibres, 
twisting  pendulums,  and,  on  setting  the  needle  in  motion, 
observed  that  the  oscillations  which  occurred  are  more  rapid 
Avhen  the  muscle  is  under  form  No.  1  than  under  form  No. 
2 ;  in  other  words,  in  experimenting  on  form  No.  2  a  slack- 
ening was  observed,  which  indicates  a  less  degree  of  elastic- 
ity and  cohesion,  the  rapidity  of  the  twirling  of  the  needle 
being  always  in  proportion  to  the  elastic  force  of  the  twisted 
thread.  , 

2.  By  a  second  experiment  Weber  ascertained  that  a  weight 
suspended  to  a  muscle  under  form  No.  2  stretched  it  more 
than  when  it  was  attached  to  that  of  another  under  form 
No.  1.  We  can  easily  understand  that  the  greater  the 
weight  the  greater  the  elongation,  and  that,  by  constantly 
adding  to  the  weight,  we  at  length  give  the  muscle  under 
form  No.  2  a  length  equal  to  that  which  it  would  have  under 
form  No.  1,  even  equal  to  its  length  under  this  form,  if 
stretched  out  by  the  same  weight ;  and,  finally,  even  to  a 
greater  length  than  if  stretched  out  by  the  same  weight 
under  form  No.  1.  On  arriving  at  the  weight  which  yields 
this  last  result,  we  notice  an  apparently  paradoxical  phenom- 
enon, which  is,  that  by  loading  with  this  weight  a  muscle 
under  form  No.  1,  and  then  making  it  pass  by  some  excita- 
tion into  form  No.  2,  we  find  that,  instead  of  shortening 
under  the  influence  of  the  weight,  on  the  contrary  it  length- 
ens, which  is  simply  the  result  of  the  muscle  under  form 


76  CONTRACTILE  ELEMENTS. 

Ko.  2  being  more  slightly  elastic,  or  less  resisting,  than  under 
form  No.  1.  This  singular  phenomenon  of  a  muscle  which 
lengthens  while  contracting  proves,  that  what  is  called  the 
active  state  (form  No.  2)  has  nothing  to  do  with  the  shrink- 
ing, and  justifies  the  selection  that  we  have  made  in  using 
the  expressions,  muscle  under  form  No.  1  and  JVb.  2,  in 
preference  to  speaking  of  contracted  or  retracted  muscles. 

Thus,  in  form  No.  2  the  elasticity  of  the  muscle  is  slight 
and  perfect,  less  even  than  under  form  No.  1. 

These  propositions  appear  in  singular  contradiction  to  what 
is  commonly  observed  in  that  condition  which  we  call  a  con- 
tracted muscle,  that  is,  one  which  has  passed,  or  rather,  is 
passiyig,  into  form  No.  2.  Any  one  may  prove  for  himself 
that  the  biceps,  for  instance,  when  contracted  is  exceedingly 
hard,  and  appears  to  be  strongly  elastic,  that  is,  offering 
great  resistance  when  drawn  out,  so  that  we  can  hardly 
believe  in  the  softness  of  the  muscle  under  the  second  form. 
This  is  because,  on  account  of  their  arrangement  with  regard 
to  the  skeleton,  the  muscles  in  the  living  body  hardly  ever 
attain  the  second  form  any  more  than  the  first  (see  above, 
tonicity).  When,  for  instance,  the  biceps  passes  into  the 
second  form,  it  has  a  tendency  to  grow  shorter  hy  five-sixths 
of  its  length;  but  the  displacement  which  it  may  cause  to 
the  bones  allows  it  to  shorten,  at  the  most,  by  only  one-sixth 
or  two-sixths ;  we  have  then  a  muscle  of  the  second  form, 
forcibly  drawn  out,  exactly  like  a  strip  of  india-rubber 
stretched  violently ;  it  is  necessarily,  then,  extremely  hard  and 
resisting  to  the  touch.  This  hardness  is  not  caused  by  the 
muscle  being  in  the  second  form,  but  by  this  form  being 
forced,  and  not  perfectly  attained;  it  does  not  arise  from  the 
contraction  of  the  muscle,  but  from  the  tension  that  it  under- 
goes during  its  contraction.  This  hardness  is  to  the  second 
form  what  the  so-called  tonicity  was,  in  a  less  degree,  to  the 
first  form. 

In  order  that  a  muscle  may  take  the  second  form  perfectly, 
the  bones  must  be  disarticulated,  or  the  muscle  must  be  cut 
at  one  of  its  insertions,  after  which  it  will  be  seen  to  shorten 
considerably,  at  the  same  time  growing  broader  (see  Fig.  18, 
p.  69).  We  have  mentioned  this  already,  when  speaking  of 
the  form  of  the  muscles  of  the  thigh,  which  are  in  a  state  of 
tetanus  after  amputation.  Being  then  subjected  to  traction, 
the  muscle  hardens,  and  as  the  forcible  elongation  increases 
the  resistance  becomes  greater,  exactly  as  with  a  strip  of 
india-rubber.    Let  this  elongation  be  caused  by  the  relation 


STRIATED  MUSCLE.  77 

of  the  muscle  to  the  resisting  skeleton,  and  in  the  case  of 
the  hardening  of  the  biceps,  which  we  took  for  an  example, 
we  shall  find  that  it  is  not  a  feature  of  the  second  form,  but 
of  the  elongation  which  the  muscle  undergoes,  and  thus  pre- 
A'^ents  it  from  assuming  that  form. 

These  considerations  show  that  the  name  of  active  muscle^ 
applied  to  the  muscle  in  the  second  form,  is  eitremely  im- 
proper. The  muscle  is  no  more  active  under  this  form  than 
under  the  first,  when  this  form  is  easily  assumed ;  and  when, 
moreover,  if  the  muscle  meets  with  resistance,  it  might  then 
be  said  to  be  passive^  like  a  strip  of  india-rubber,  which  can- 
not be  said  to  be  active  because  it  shows  a  tendency  to 
return  to  that  form  from  which  it  was  diverted  by  being 
stretched.  The  only  activity  of  the  muscle  consists  in  its 
passage  from  the  first  to  the  second  form ;  but  in  each  of 
these  forms  it  is  passive,  because  its  insertions  constrain  it  as 
much  in  the  former  as  in  the  latter  case. 

Chemical  Phenomena.  —  We  have  seen  that  the  muscle, 
under  the  first  form,  absorbs  oxygen,  and  gives  off  carbonic 
acid ;  that  it  is,  in  short,  the  seat  of  combustion,  the  materi- 
als for  which  are  furnished  by  the  blood.  The  same  is  true 
of  the  second  form,  with  the  exception  that,  in  this  case,  the 
combustion  is  much  m,ore  active;  thus,  on  analyzing  the 
products  evolved  by  a  muscle  which  has  been  made  to  pass 
into  the  second  form,  or  on  examining  the  waste  of  any 
entire  organism  during  severe  muscular  labor,  we  find  a 
greater  absorption  of  oxygen  and  evolution  of  carbonic 
acid.  Combustion  then  appears  to  be  sufficiently  active  for 
the  formation  of  acids,  so  that  in  a  muscle  which  is  fatigued, 
that  is,  which  remains  long  in  the  second  form,  the  muscular 
fluid  becomes  less  and  less  alkaline,  and  at  length  completely 
acid  :  the  acid  thus  formed  is  called  sarcolactic  acid. 

The  combustion  which  takes  place  in  the  muscle  is  shown 
immediately  by  the  aspect  of  the  blood  which  flows  from  it, 
and  which  resembles  venous  blood,  Uach  blood  (rich  in  CO^ 
and  poor  in  O),  the  resemblance  being  greater  in  proportion 
to  the  energy  of  the  muscle.  Thus,  when  all  muscular  con- 
traction ceases,  as  in  syncope,  the  venosity  of  the  blood 
diminishes  to  such  a  degree  that  the  blood  which  flows  from 
an  incision  made  in  a  vein  shows  nearly  all  the  distinguish- 
ing features  of  arterial  blood.^ 

^  Brown- Sequard,  "  Du  Sang  rouge  et  du  Sang  noir,"  1858. 
CI.  Bernard,  "  Liquide  de  I'Organisme,"  1859. 


78  CONTRACTILE  ELEMENTS. 

Tlie  materiafs  of  this  active  combustion  are  principally 
hydrocarbons,  that  is,  the  fatty  and  amyloid  substances  pro- 
duced in  the  blood ;  in  other  words,  the  aliments  called 
respiratory,  for  the  muscle  oxidizes  scarcely  any  nitrogenous 
substances,  and  muscular  labor  causes  scarcely  any  increase 
in  the  excretion  of  the  urea.^ 

*  The  fact  that  the  muscle,  when  at  work,  consumes  principally 
hydrocarbon  aliments,  and  not  albuminoid  substances,  is  quite  a 
recent  acquisition  to  science,  and  is  a  part  of  the  knowledge  lately 
obtained  as  to  the  mechanical  equivalent  of  heat. 

Liebig  had  divided  all  aliments  into  respiratory  and  plastic.  The 
former,  by  their  combustion,  produced  animal  heat  ;  these  were 
the  fatty  substances  and  sugars,  hydrocarbons,  in  short:  the  latter, 
represented  by  the  albuminoids,  were  intended  to  repair  the  tis- 
sues, especially  the  muscles.  As  to  muscular  labor,  it  was  j^ro- 
duced  by  the  muscle  at  the  cost  of  its  own  substance,  the  albuminoid 
aUments  thus  alone  supplying  the  material  for  it. 

The  new  ideas  as  to  mechanical  labor,  and  its  relations  to 
heat,  derived  from  the  researches  of  Rumford,  of  Tyndall,  of 
Joule  (Manchester),  of  Mayer  (Bonn),  and  Hirn  (Logelbach), 
showed  that  heat  and  mechanical  labor  are  the  same  thing,  or,  at 
least,  are  two  equivalent  forces;*  that  one  is  transformed  into  the 
other,  according  to  the  law  of  the  equivalence  and  constancy  of  forces., 
and  that,  for  instance,  a  calorie  may  be  made  to  produce  425  kilo- 
grammetres;  that  is  to  say,  that  the  great  heat  which  raises  one 
kilogramme  of  water  one  degree  can  also,  under  another  form 
(labor),  raise  a  weight  of  one  kilogramme  to  the  height  of  425 
metres :  thus  the  number  425  expresses  the  mechanical  equivalent  of 
heat. 

Now  the  muscle  is  also  a  machine ;  it  transforms  heat  into  me- 
chanical labor  (see  the  text,  some  lines  farther  on),  only  it  is  a 
more  perfect  machine,  than  any  manufactured  one,  a  machine 
which,  with  a  much  smaller  weight,  transforms  into  labor  a  far 
larger  part  of  the  heat  produced  (one-fifth  in  place  of  one- tenth, 
as  given  by  the  best  steam  engines). 

If,  then,  we  consider  muscular  labor  as  transformed  heat,  its 
source  must  lie  in  the  combustions  which  produce  heat,  and  the 
muscle  must  be  looked  upon,  not  as  an  apparatus  which  consumes 
its  own  substance,  but  as  one  which  serves  as  a  place  of  combustion 
for  the  materials  which  produce  heat  or  labor.  This  was  the  hypoth- 
esis put  forth  by  Mayer,  in  1845,  when,  relying  on  the  principle 
of  the  constancy  of  forces,  he  first  looked  upon  heat  and  muscular 
labor  as  manifestations  of  living  forces,  and  considered  them  as 
emanating  from  one  and  the  same  origin,  combustion. 

From  that  time  the  division,  as  made  by  Liebig,  of  aliments 

*  See  Paul  Bert:  Article  "Chaleur,"  in  the  "Nouveau  Dictionnaire  de  M^de- 
eine  et  de  Chirurgie  Pratiques,"  Vol.  VI. 


STRIATED  MUSCLE.  79 

We  see,  thus,  that  mnscular  contraction  (or  the  passage  of 
the  muscle  from  the  first  to  the  second  form)  must  be  reck- 
oned first  among  the  sources  of  animal  heat,  on  account  of 
the  active  combustion  which  is  then  produced.     If,  indeed,  a 

into  respiratory  and  plastic,  attributing  to  the  latter  (albuminoids) 
the  source  of  muscular  labor,  could  only  be  admitted  after  direct 
proof.  Reasoning  first  led  to  the  belief  that  muscular  labor,  behig  a 
form  of  heat,  must  derive  its  origin  from  ahments  whose  combus- 
tion furnishes  the  greatest  degree  of  heat,  as  the  fats  and  hydro- 
carbons. And  Mayer  calculated  that  if  it  was  true  that  the  muscle 
consumes  either  its  own  substance  or  albuminoids  (which  comes  to 
the  same  thing),  the  heat  developed  by  the  oxidation  of  these  sub- 
stances is  so  trifling  that  a  man  would  have  entirely  consumed  his 
muscular  mass  after  a  few  days'  labor. 

The  question  could  only  be  decided  by  direct  experiment,  and 
the  proof  needed  was  very  simple.  We  shall  see  farther  on  that 
the  residuum  of  combustion  of  the  albuminoids  is  essentially  con 
stituted  by  the  urea  eliminated  by  the  kidneys;  if,  during  mechan- 
ical labor,  a  large  amount  of  albuminoids  are  consumed,  there  will 
be  a  great  increase  of  urea  in  the  urine. 

After  some  unsatisfactory  experiments  by  Lehmann  and  Speck, 
and  some,  more  conclusive,  by  Bischoif  and  Vogt,  Fick  and  Wis- 
licenus  solved  the  problem  in  a  remarkable  manner.  These  two 
physiologists  ascended,  fasting,  one  of  the  high  mountains  of  the 
Bernese  Alps,  measuring  carefully  the  quantity  of  urea  eliminated 
by  the  kidneys  during  and  after  the  ascent.  In  the  case  of  one  of 
them  the  labor  developed  by  this  ascent  may  be  represented  by 
184  287  kilogrammetres,  yet  no  increase  in  the  urea  was  observed 
either  during  or  after  this  very  severe  muscular  exercise.  AVe  see 
thus  that  the  muscle,  as  the  source  of  labor  or  heat,  consumes  only 
hydrocarbons  and  fats,  and  not  albuminoids. 

To  this  satisfactory  experiment  may  be  added  some  considera- 
tions of  comparative  physiology.  The  herbivorous  animals,  that 
is,  those  which  feed  principally  on  hydrocarbons,  are  capable  of 
develoj)ing  a  much  greater  degree  of  force  than  the  carnivora, 
which  are  nourished  by  albuminoids;  thus  man  for  mechanical 
labor  makes  use  only  of  the  herbivorous  animals  (the  horse,  the 
ox).  The  granivorous  birds  are  in  general  more  active,  and 
develop  more  heat  and  labor,  than  the  carnivorous.  This  fact  is 
still  more  striking  in  the  case  of  insects:  thus,  among  the  acari 
some  live  as  parasites  on  animals,  while  others  feed  on  flour  or 
sugar  (for  instance,  Glyciphagi);  the  former  being  remarkable 
for  the  slowness,  and  the  latter  for  the  almost  incredible  rapidity 
of  their  movements.  An  experiment  of  this  kind,  in  regard  to 
food,  has  also  been  made  upon  man.  An  Englishman,  Harting, 
found,  after  submitting  to  a  regimen  of  fifteen  hundred  grammes 
of  meat  a  day,  with  scarcely  any  hydrocarbons,  that  he  was  re- 
duced to  an  ♦extreme  degree  of  muscular  weakness. 


80  CONTRACTILE  ELEMENTS. 

muscle  in  which  contraction  occurs  passes  perfectly  into  the 
second  form  without  meeting  with  any  obstacle,  it  gives  rise 
to  heat  only ;  but  if,  as  in  the  normal  condition,  it  cannot 
perfectly  attain  this  form,  on  account  of  the  resistance  which 
it  has  to  overcome,  we  find  that,  on  hardening,  it  evolves 
only  a  part  of  the  heat  produced  by  the  combustion  of  which 
it  is  the  seat,  the  rest  being  transformed  into  mechanical 
labor  (B^clard). 

Electro-motor  Power,  —  We  have  seen  that  under  the 
first  form  the  muscle  possesses  an  electro-motor  power,  by 
means  of  which  its  surface  is  positive,  in  relation  to  its  in- 
terior. 

If  the  wires  of  a  galvanometer  are  placed  in  contact  with 
a  muscle  under  the  first  form,  one  with  its  surface  or  longi- 
tudinal section,  the  other  with  its  transverse  section ;  so  as  to 
ascertain  the  current,  which  in  this  case  is  directed  from  the 
former  surface  to  the  latter  in  the  galvanometrical  circuit, 
and  the  muscle  is  then  made  to  pass  into  the  second  form ;  we 
find  that  the  needle,  which  the  current  at  first  caused  to 
swerve,  returns  to  zero,  and  oscillates  on  this  side  and  above 
it  (Du  Bois-Keymond).  Thus  the  electro-motor  condition 
of  the  muscle  is  changed  :  this  is  what  is  called  negative 
variation  of  the  current  of  a  contracted  muscle.  But,  as 
we  have  seen  that  no  conclusion  can  be  drawn  from  the 
electro-motor  power  of  the  muscle  under  its  first  form,  so 
nothing  positive  can  be  afiirmed  as  to  its  negative  variation 
in  the  second  form,  for  it  is  still  impossible  to  say  whether 
the  latter  is  due  to  the  suppression  of  the  primitive  current, 
to  its  simple  diminution,  or  even  to  its  being  replaced  by  a 
contrary  current. 

Du  Bois-Reymond,  who  discovered  negative  variation, 
considered  this  phenomenon  as  the  result  of  the  weakening 
of  the  normal  current  (electro-motor)  of  the  muscle  when  in 
the  state  of  repose,  which  weakening  would  allow  of  the 
manifestation  of  a  contrary  current,  due  only  to  the  second- 
ary polarities  of  the  wire  of  the  galvanometres  (polarization 
of  the  electrodes.  —  See  Wundt's  "Physique").  Matteucci 
believed,  on  the  contrary,  in  a  complete  inversion  of  the  nor- 
mal current  of  repose.  Experience  has  shown  that  Du  Bois- 
Reymond  was  right,  for,  by  constructing  electrodes  which 
undergo  no  polarization  (amalgamated  zinc,  dipped  in  a 
solution  of  sulphate  of  zinc,  Regnault),  it  has  been  proved 
that,  when  the  muscle  passes  into  the  second  form,  there 
results  only  suppression,  or  even  only  diminution,  but  never 


STRIATED  MUSCLE.  81 

inversion,  of  the  normal  current  of  the  muscle  under  the 
first  form. 

C.  Hole  of  the  Muscle  in  the  System  :  its  Function. 

Knowing  the  two  forms  of  the  muscle,  and  the  properties 
whicli  it  enjoys  under  each,  we  can  now  form  some  idea  of 
tlie  manner  in  which  the  muscular  element  works  in  the 
organism.  The  properties  of  the  muscle  which  are  of  most 
use  in  the  system  may  be  said  to  be : 

1.  Its  Elasticity.  —  We  shall  see,  farther  on,  that  many 
of  the  cavities  with  muscular  coats  profit  more  especially  by 
the  perfect  elasticity  of  the  muscle,  and  the  really  wonderful 
tendency  to  distension  which  it  shows.  With  regard  to  the 
stomach  and  the  auricles  of  the  heart,  we  shall  see,  in  par- 
ticular, that  the  muscle,  placed  in  the  coats  of  these  mem- 
branous bags,  is  especially  useful,  on  account  of  the  great 
ease  with  which  it  enables  these  cavities  to  expand,  and  we 
shall  have  no  hesitation  in  admitting  that  the  muscles  (the 
pulmonary  alveoli,  for  instance,  or  at  least  the  bronchi)  act 
much  more  by  their  elasticity  than  by  their  contractility. 

2.  TJie  property  of  passiny  from  the  first  to  the  second 
form  constitutes  the  real  vital  activity,  the  essential  physio- 
logical property,  of  the  muscular  element :  in  this  lies  its 
irritability.  We  must,  therefore,  study  this  irritability,  in 
order  to  see  if  it  is  really  a  property  of  the  muscle,  similar 
to  that  which  we  have  described  in  the  globules;  what  are 
the  agents  whicli  modify  it ;  the  irritants  which  bring  it  into 
play ;  how  the  muscle  responds  to  these  irritants ;  and,  finally, 
how  we  can  undertake  an  explanation  of  the  inward  changes 
which  then  take  place  in  the  muscle. 

Irritability  of  the  Muscle.  —  According  to  the  course 
which  we  have  followed,  showing  that  from  the  globule ; 
which  is  the  first  form  of  all  the  tissues  and  the  source  of  all 
vital  phenomena,  the  anatomical  form  and  the  physiological 
properties  of  the  muscular  element  are  derived ;  we  can  easily 
conceive  that  the  muscle  preserves  the  same  method  of  irri- 
tability as  the  globule,  and  that  the  property  of  thus  react- 
ing, under  the  influence  of  excitants,  is  quite  characteristic 
of  it.  This  has  not  been  the  method  employed  by  all 
physiologists,  and,  although  Ilaller  had  already  shown 
irritability  to  be  a  property  inherent  in  the  muscle  itself, 
many  authors  have  since  maintained,  and  maintain  still,  that 
the  muscle  is  not  directly  irritable  (Funke,  Eckhard,  Jac- 
coud),  and  that  all  excitants  applied  to  the  muscle  act  upon 

6 


82  CONTRACTILE  ELEMENTS. 

it  only  by  the  intermediation  of  terminations  of  the  motor 
nerves  which  it  contains.  Of  the  numerous  facts  which 
refute  this  theory,  and  demonstrate  the  direct  irritabiUty  of 
the  muscle,  w^e  will  mention  only  the  two  following : 

There  are  certain  poisons  (woorara)  which  render  the 
motor  nerves  completely  incapable  of  action,  and,  conse- 
quently, powerless  to  convey  any  irritation  to  the  muscles ; 
and  yet,  in  this  case,  the  muscles  which  are  directly  excited 
can  pass  from  the  first  to  the  second  form  (CI.  Bernard, 
Kolliker) ;  the  ultimate  and  fine  ramifications  of  nerves 
which  they  contain  are  not  affected  by  this  irritability,  for 
the  poisons  in  question  deprive  of  vitality  especially  the  intra- 
muscular terminations  of  the  nerves  (Vulpian). 

A  motor  nerve  separated  from  the  cerebro-spinal  axis  loses 
all  excitability  after  four  days :  the  muscle,  on  the  contrary, 
previously  innervated  by  this  nerve,  is  still  directly  excitable 
more  than  three  months  after  (if  only  its  connection  has 
been  kept  up  with  the  sensitive  nerves,  and  the  vaso-motors, 
which  provide  for  its  nutrition.     Longet). 

Variations  of  Irritability.  —  This  irritability  belongs, 
thus,  really  to  the  muscle  itself,  but  it  is  modified  by  dif- 
ferent circumstances,  all  of  which  may  be  said  to  modify  the 
nutrition  of  the  muscle,  or  its  chemical  composition.  This 
is  the  eflfect  of  too  prolonged  repose.  Moderate  exercise, 
which  causes  a  greater  interchange  between  the  muscle  and 
the  blood,  keeps  up  the  nutrition  of  the  muscle,  while  a  con- 
trary eflTect  is  produced  by  fatigue  or  permanent  contraction, 
by  means  of  which  acids  accumulate  in  the  muscle,  and  the 
alkalinity  necessary  to  the  preservation  of  its  properties  is 
lost;  thus,  a  short  time  after  death  the  muscle  ceases  to  be 
irritable,  the  circulation  no  longer  furnishing  the  materials 
necessary  to  its  support.  The  period  at  which  the  irritability 
disappears  varies  in  difierent  animals,  being  apparently  shorter 
in  those  whose  nutrition  is  most  active ;  that  is,  in  those  whose 
muscle  consumes  most  quickly  the  materials  left  by  the  cir- 
culation :  the  time  being  considerably  longer  in  the  case  of 
the  cold-blooded  animals.  It  varies,  however,  in  an  animal, 
in  diflTerent  muscles,  and  even  in  difierent  parts  of  the  same 
muscular  organ  :  thus  the  left  ventricle  of  the  heart  is  one  of 
the  first  muscles  to  die,  while  the  right  auricle  keeps  its  irri- 
tability longer  than  any  other  muscle  of  the  body,  and  has 
thereb}''  gained  the  name  of  ultimum  moriens. 

Cadaveric  Rigidity.  —  The  muscle,  having  lost  its  irrita- 
bility, passes  into  the  state  which  we  have  already  spoken  of 


■ 


STRIATED  MUSCLE.  83 

under  the  name  of  cadaveric  rigidity,  which  rigidity  is 
owing  to  the  coagulation  of  the  albuminous  substance  of  the 
muscle  (myosin)  by  the  acids  which  it  has  formed.  The 
muscle  may  also  pass  into  the  state  of  spontaneous  rigidity^ 
after  a  continued  activity  which  produces  great  excess  of 
acid :  mineral  acids,  heat  50®  c,  any  thing,  in  short,  which 
coagulates  the  myosin,  either  produces  or  hastens  this  rigid- 
ity. We  have  already  remarked  that  an  injection  of  serum 
or  of  alkaline  liquid  entirely  prevents  or  delays  it  (p.  71). 
The  sort  of  retraction  which  the  muscles  undergo  during 
this  rigidity  is  owing  to  the  contraction  or  solidification  of 
the  coagulated  myosin ;  the  muscle  is  then  extremely  fragile, 
and  only  ceases  to  be  so  when  the  coagulum  becomes  lique- 
fied by  putrefaction.  Of  course,  the  muscle  then  becomes 
alkaline  again  by  means  of  the  ammonia  resulting  from  its 
decomposition. 

JrnYa/i^s.  7- The  agents  which  excite  the  irritability  of 
the  muscle  are  very  numerous.  As  their  mode  of  action  is 
not  exactly  known,  they  have  been  divided  and  classed 
simply  as  chemical,  physical,  and  physiological. 

The  chemical  excitants  are  very  numerous;  almost  any 
chemical  agent  can  cause  a  muscle  to  pass  from  the  first  into 
the  second  form.  We  will  only  observe  that  these  agents 
must,  in  general,  be  very  much  diluted,  and  that  some  among 
them,  ammonia,  for  instance,  have,  when  thus  diluted,  no 
influence  upon  the  motor  nerves,  which  is  a  fresh  proof  that 
muscular  irritability  belongs  really,  not  to  the  nerves,  but  to 
the  muscles. 

Among  physical  excitants  we  must  rank  first,  electricity, 
and  especially  currents,  whatever  be  their  source  (see  p.  30)  ; 
other  physical  excitants,  often  employed  in  experiments,  are 
pinching,  a  blow  (Heidenhain),  or  pricking.  Most  people 
have  seen  how  fresh  meat,  in  a  butcher's  stall,  will  palpitate 
under  the  influence  of  a  current  of  air,  a  breath  of  wind. 
Changes  of  temperature,  especially  cold,  must  also  be  reck- 
oned among  these  excitants :  cold  is  often  employed  in  sur- 
gery to  produce  contraction  of  the  smooth  muscular  elements 
of  the  arteries  (see  circulation ;  physiology  of  the  arterial 
coats).  Indeed,  light  itself  is  an  excitant  of  muscle,  as  has 
been  shown  by  Brown-Sequard,  in  his  experiments  on  the 
pupil  of  the  eye. 

Finally,  the  physiological  excitant,  whose  object  in  the 
organism  is  to  make  the  muscle  pass  from  the  first  into  the 
fifecond  form,  is  represented  by  the  action  of  the  motor 
erves. 


84  CONTRACTILE  ELEMENTS. 

Analysis  of  Contraction.  —  The  muscle,  after  obeying 
these  irritants,  and  pnssing  from  the  lirst  into  the  second 
form,  returns  to  the  first ;  this  succession  of  changes  is  what 
is  called  the  contraction  of  the  muscle.  It  is  made  up  of 
several  periods :  that  during  which  the  muscle  passes  into 
the  second  form;  the  time  during  which  it  remains  in  it; 
and,  finally,  that  occupied  by  its  return  to  the  first.     It  has 


r\ 


\ 


-fXX 


Ilg.  20.— Kymo-graphic  tracings  of  muscular  contraction.* 

been  also  discovered  that,  when  an  excitant  acts  upon  a 
muscle,  a  short  space  of  time  elapses  before  the  latter 
responds  to  the  excitation  (Helmholtz).  This  forms  a  period 
preceding  the  three  others,  and  is  called  latent  excitation. 

*  Ij  Analysis  of  dia^am  representing^  muscular  contraction.  AB,  Latent 
excitation.  fiC,  Line  of  ascent.  CD,  Line  drawn  during  the  continuance  of 
form  No.  2.    D  K,  Line  of  descent  and  return  to  form  No.  1  (E  F). 

2,  Ordinary  form  of  a  jerk  {secousse).  A  B,  Latent  excitation.  From  B  to 
C  D,  ascent,  or  passage  from  form  No.  1  to  form  No.  2 ;  the  latter  lasts  for  a 
moment  only  in  C  D,  and  is  immediately  followed  by  the  line  of  descent,  D  E, 
or  return  to  form  No.  1  (E  F). 

3,  Physiological  tetanus.  AB,  Latent  excitation.  BC,  Ascent.  CE,  De- 
scent interrupted  by  a  fresh  ascent ;  the  jerks  {secouases)  thus  produced  in  suc- 
cession (c,  c',  </',  c''''),  afterwards  succeed  each  other  so  rapidly  as  to  become 
blended  in  one,  causing  the  muscle  to  retain  the  form  No.  2,  and  to  describe  the 
line  F.  The  dotted  lines  indicate  the  descents  or  return  to  tlie  form  No.  2,  which 
would  take  place  if  fresh  excitations  did  not  force  the  muscle  to  describe  a  new 
line  of  ascent  before  it  has  had  time  to  complete  the  line  of  descent  produced  br 
the  preceding  jerk  {stcousst). 


1 


STRIATED  MUSCLE.  85 

If  a  muscle  be  suspended  vertically  by  one  extremity,  hav- 
ing fastened  to  it  at  the  other  a  pencil  which  makes  a  mark 
upon  a  vertical  cylinder  revolving  regularly,  so  long  as 
the  muscle  is  under  the  first  form  a  horizontal  line  will  be 
traced  upon  the  cylinder.  Should  any  excitant  act  upon  the 
muscle,  it  will  still  continue  for  a  certain  time  to  trace  a 
straight  line,  and  this  tracing  will  represent  graphically  the 
period  of  latent  excitation  (Fig.  19, 1,  2,  and  3,  A  B).  As  the 
muscle  passes  into  the  second  form,  its  lower  extremity  will 
trace  an  ascending  line  (Fig.  19,  B  0),  representing  the  pas- 
sage from  one  form  to  the  other ;  at  the  level  attained  by 
this  line  we  shall  find  that  a  new  horizontal  line  begins, 
representing  the  time  during  which  the  second  form  lasts ; 
finally  will  come  a  descending  line,  representing  the  return 
to  the  first  form  (DE).  The  various  instruments  called 
myographs  are  constructed  on  this  principle  (Helmholtz, 
Marey) ;  and  in  this  way,  also,  have  been  obtained  the 
recorded  writings  of  muscular  contraction^  with  analysis 
of  the  different  periods. 

If  we  examine  by  this  means  the  contraction  of  a  muscle, 
which  follows  a  short  and  sudden  irritation  (a  blow,  for 
instance),  we  find  in  the  record  that  the  descent  immediately 
follows  the  ascent  (Fig.  19,  2,  CD),  which  shows  that  the 
second  form  has  existed  only  for  a  short  time,  and  is  there- 
fore represented,  not  by  a  line,  but  simply  by  a  point,  mark- 
ing the  passage  from  the  ascent  to  the  descent.  This  is 
called  the  jerk^  or  muscular  convulsion.  But  when  short 
and  sudden  excitations  succeed  each  other  rapidly,  we  see, 
by  the  diagram,  that  a  new  contraction  begins  before  the 
descent  of  the  first  is  finished  (Fig.  19,  3,  c,  c',  c"^  c'")  ;  that 
is,  the  muscle,  beginning  to  return  to  the  first  form,  has  been 
again  induced  to  take  the  second ;  these  half-descents,  inter- 
rupted by  a  new  ascent,  are  therefore  marked  upon  the  dia- 
gram by  a  series  of  undulating  lines ;  they  approach  nearer 
the  corresponding  level  of  the  second  form,  when  these 
excitations  succeed  one  another  more  rapidly  (Fig.  19,  3,  line 
F).  We  can  easily  conceive  that  the  closer  the  excitations 
follow  each  other,  the  shorter  the  undulations  will  be  marked, 
until  at  length  they  form  a  straight  line,  lasting  as  long 
as  the  excitations  continue  to  take  place  with  the  same 
rapidity ;  the  muscle  all  this  time  will  maintain  the  second 
form. 

This  preservation  of  the  second  form,  considered  as  the 
result  of  a  succession   of  jerks   (secousses)   or  continuous 


86  CONTRACTILE  ELEMENTS, 

convulsions,  is  what  has  been  called  2i  physiological  tetanus 
(Ed.  Weber).  Thirty  excitations  a  second  are  usually  re- 
quired to  produce  this.  This  result  leads  us  to  believe  that 
the  contracted  muscle,  as  we  generally  find  it  in  the  living 
animal,  remains  for  a  certain  time  in  the  second  form,  only 
by  means  of  a  succession  of  continuous  shocks ;  in  fact,  if  a 
muscle  in  this  state  be  ausculted,  a  sound  is  heard,  the  mus- 
cular tone,  the  height  of  which  corresponds  to  about  thirty 
vibrations  a  second,  which  is  exactly  the  number  of  excita- 
tions, and,  consequently,  of  muscular  shocks,  needed  to  pre- 
serve the  second  form,  or  experimental  physiological  tetanus 
(WoUaston,  Helmoltz). 

If,  by  means  of  thirty  excitations  a  second,  the  shocks  be 
rendered  simultaneous,  producing  permanent  contraction  (or 
physiological  tetanus),  and  the  rapidity  of  the  excitations  be 
then  increased,  the  force  of  the  contraction  increases  also  j 
and,  since  the  tone,  or  muscular  sound,  becomes  sharper  and 
higher,  it  is  proved  that  the  contraction  is  composed  of  a 
gi-eater  number  of  blended  jerks  or  shocks.  This  may  be 
easily  verified  by  listening  one's  self  to  the  sound  of  the 
masseter  when  more  or  less  strongly  contracted.  This  sound, 
heard  in  the  perfect  stillness  of  the  night,  sometimes  rises  as 
high  as  a  fifth  (Marey). 

If  the  muscle  be  fatigued,  the  shocks  are  more  easily 
blended  together,  but  the  force  of  the  contraction  is  dimin- 
ished (Marey). 

There  are  certain  striated  muscles  in  which  the  shock 
takes  place  very  slowly;  in  other  words,  their  curve  of  con- 
traction is  very  long.  Such  is  the  case  with  the  muscles  of 
the  tortoise  and  the  muscular  fibres  of  the  heart  (Marey). 
The  latter  form  a  sort  of  transition  between  the  striated 
and  the  smooth  muscles,  the  shock  of  which  is  very  long, 
and  is  represented  in  a  diagram  by  the  line  of  physiological 
tetanus. 

If  a  weight  be  attached  to  the  extremity  of  a  muscle  at 
the  instant  when  a  shock  takes  place,  or  during  the  physio- 
logical tetanus,  the  weight  will  be  raised,  unless  it  be  too 
great  (see  pp.  75  and  76).  This  constitutes  the  labor  of  the 
muscle,  and  it  is  in  this  way  that  its  force  is  measured. 

The  height  to  which  a  muscle  can  lift  any  weight  depends 
on  the  length  of  its  fibres ;  but  what  is  meant  by  its  force  of 
contraction  {absolute  muscular  force)  is  measured  by  the 
weight  requisite  for  the  neutralization  of  the  movement,  and 
depends  only  on  the  extent  of  the  transverse  section  of  the 


STRIATED  MUSCLE.  87 

muscles,  or  on  the  number  of  fibres  of  which  they  are  com- 
posed. Rosenthal  discovered,  in  experimenting  on  the 
muscles  of  a  frog,,  that  the  contracting  force  of  the  adduc- 
tor muscles  in  the  thigh  of  this  animal  varies  (in  the  whole 
transverse  section,  that  is,  one  square  centimetre)  from  two 
to  three  kilogrammes.  In  the  gastrocnemii  and  soleus  in 
man  it  is  about  eight  kilogrammes  to  a  square  centimetre. 
This  experiment  is  easily  made  on  man.  The  person  to  be 
experimented  upon  stands  upright,  and  such  a  weight  is 
placed  upon  his  body  as  to  render  it  quite  impossible  for  him 
to  rise  upon  his  toes  or  raise  his  heels  from  the  ground.  At 
this  moment  the  weight  of  the  body,  with  the  weight  added 
to  it,  plainly  represents  the  force,  or  weight  necessary  to 
neutralize  the  movement  which  the  muscles  of  the  calf  have 
a  tendency  to  produce  when  the  person  rises  upon  the  toes, 
or,  better  still,  on  the  extremities  of  the  metatarsals.  The 
exact  force  of  the  muscles  of  the  calf  is  thus  equal  to  the 
value  of  this  weight  divided  by  the  length  of  the  lever  arm 
(see  farther  on,  mechanism  of  the  skeletoit:  lever  of  the 
second  kind) ;  given,  then,  the  mean  transverse  section  of 
the  muscular  mass  of  the  calf  (gastrocnemii  and  soleus),  it  is 
easy  to  deduce  from  it  the  exact  force  of  the  whole  surface 
of  these  muscles. 

The  total  weight  of  the  mass  of  the  muscles  in  man 
shows  that,  in  a  mechanical  point  of  view,  these  organs  form 
machines  quite  powerful  and  perfect ;  and  that,  in  proportion 
to  their  weight,  which  is  comparatively  very  light,  they 
develop  a  miich  greater  force  than  any  machine  that  we  can 
construct.^ 

Physiologists  have  analyzed  still  more  closely  the  phenom- 
enon presented  by  the  passage  from  the  first  to  the  second 
form,  and  have  sought  to  discover  the  molecular  modifica- 
tions which  take  place  in  the  muscular  fibre  during  this  phe- 
nomenon. 

It  is  scarcely  worth  while  to  mention  the  theory  which 
explained  the  second  form  as  being  a  zigzag  folding  of  the 
muscular  fibre  (Prevost  and  Dumas,  1823),  this  theory  hav- 
ing been  proved  to  be  founded  on  an  error  in  observation. 
In  this  case  the  muscular  fibre,  being  placed  upon  a  sheet  of 
glass,  adhered  to  it  by  its  sheath,  so  that,  after  taking  the 
second  form,  it  could  not  easily  return  to  the  first,  its 
adherences  causing  it  to  bend  in  a  broken  line ;  it  is  then 

*  Weber,  Rosenthal,  Hermann. 


88  CONTRACTILE  ELEMENTS. 

only,  in  this  incomplete  return,  that  the  zigzag  form  is 
observed. 

Two  theories  now  contend  for  the  explanation  of  this  phe- 
nomenon. 

According  to  some  (Weber,  Aeby,  Marey),  the  almost 
liquid  contents  of  the  muscular  fibre  are  the  seat  of  a  sei-ies 
of  waves  {muscular  wave),  whose  presence  produces  the 
shortening  of  the  muscle,  and  its  transverse  enhxrgement. 

According  to  others  (Rouget),  the  muscular  fibres  are 
decomposed  into  smaller  and  very  numerous^^riYs,  formed 
by  a  sort  of  spiral  line.  As  the  juxtaposition  of  these  spiral 
lines  explains  the  striated  appearance  of  the  muscular  fibre, 
so  their  lengthening  or  shortening  gives  us  the  key  to  the 
first  and  the  second  form,  and  to  that  caused  by  the  passage 
from  one  to  the  other. 

Marey  has  shown  that  if  two  of  those  myographical  pincers, 
which  are  used  to  register  the  swelling  which  takes  place  in  a 
muscle  when  contracted,  be  placed  at  a  certain  distance  from 
each  other  lengthwise  upon  the  muscle,  these  two  pincers  will 
not  record  the  swelling  of  the  muscle  at  the  same  instant ;  the 
one  nearest  the  extremity  which  is  excited  acts  first,  and  then 
the  other.  The  swelling  of  the  muscle  thus  advances  like 
a  wave,  of  which  the  velocity  has  been  estimated  by  Marey 
at  one  metre  a  second.  Aeby  has,  however,  shown  that  if, 
instead  of  exciting  the  muscle  at  one  extremity  only,  it  be 
excited  throughout,  by  placing  each  extremity  in  contact 
with  one  of  the  wires  of  the  exciting  current,  or  if  the  motor 
nerve  of  the  muscle  be  excited ;  the  two  tracings  made  by 
the  myographical  pincers  are  exactly  superposed  or  syn- 
chronic. In  this  case  the  muscular  fibre  contracts  in  all  its 
pai-ts  at  once. 

Professor  Rouget  has  observed,  by  examination  of  the 
contractile  pedicle  of  the  vorticelli,  that  the  muscular  fihi-e 
is  a  true  spiral  spring  (p.  68),  which,  actively  distended  daring 
tJie  repose  of  the  muscle,  returns  upon  itself  at  the  moment 
of  contraction:  muscular  contractility  is  a  purely  physical 
property  of  elasticity ;  the  rigidity  of  a  corpse  is  a  phenom- 
enon of  the  same  order  as  muscular  contraction  in  the  living 
body.  "  The  stem,  of  the  vorticella  presents  the  principal 
organ  of  locomotion  of  an  animal,  formed  by  a  single  muscular 
fibril,  free  in  a  tube,  at  the  centre  of  a  perfectly  transparent 
sheath;  which  allows  us  to  see  with  the  greatest  distinctness 
all  the  changes  undergone  by  the  contractile  element  during 
its  state  of  activity  or  of  repose,  of  elongation  or  of  con- 


I 


STRIATED  MUSCLE.  89 


traction.  When  the  animal  is  at  rest  the  style  is  at  the 
maximum  of  elongation,  and  the  body  as  far  as  possible 
from  the  points  of  adhesion  and  of  refuge.  In  this  state  the 
central  filament  of  the  style,  the  contractile  fibril,  is  com- 
pletely extended ;  it  is,  however,  never  straight,  but  always 
twisted  in  a  long  spiral  line,  like  a  ribbon  wound  round 
its  longitudinal  axis;  which  resembles  exactly  the  spiral 
spring  of  a  watch,  fixed  and  firmly  drawn  out  at  the  extremi- 
ties. 

"  At  the  instant  that  any  mechanical,  electrical,  or  thermi- 
cal  excitant  touches  the  animal,  this  elongated  spiral  line, 
returning  suddenly  upon  itself,  is  transformed  almost  instan- 
taneously into  a  spiral  spring  of  perfect  uniformity,  the  coils 
of  which  are  very  near  each  other,  measuring  not  much  more 
than  a  fifth  of  the  length  of  the  style  when  in  repose,  while 
their  transverse  diameter  is  proportionately  increased.  This 
state  lasts  generally  only  for  a  short  time ;  the  coils  of  the 
spring  withdraw  from  each  other,  the  spring  lengthens  out 
slowly,  and  the  animal  returns  to  its  former  position. 

"  The  shortening  or  lengthening  of  the  contractile  organ 
is  here  evidently  owing  to  the  junction  or  separation  of  the 
coils  of  a  spiral  spring.  But  which  of  these  two  states  is  that 
which  brings  the  elasticity  into  play  ?  In  which  do  we  find 
the  muscular  spring  returned  to  its  natural  form,  the  state  of 
repose  ?  In  the  first  place,  observation  has  established  this 
important  fact,  that  the  spiral  filament  is  never  found  at  its 
extreme  elongation  unless  the  animal  is  alive  and  uninjured. 
If  the  animal  be  killed,  or  the  style  detached,  the  coils  of  the 
spring  roll  up  into  a  tendril,  and  remain  in  this  state :  the 
case  is  the  same  if  the  animal  be  killed  by  any  poisonous 
agent,  or  by  raising  the  temperature  to  -{-  40  or  45*^  (C).  It 
frequently  happens,  during  the  lifetime  of  the  animal,  that 
the  contractile  fibril  is  severed,  and  thus  the  continuity 
between  it  and  the  body,  or  the  trophical  centre  of  the  whole 
animal,  broken :  in  this  case,  although  the  sheath  is  perfect, 
the  body,  living  and  swimming  by  means  of  the  vibratile 
cilia,  drags  at  its  inferior  part  the  dead  contractile  fibril, 
rolled  up  like  a  tendril,  having  tor  ever  lost  the  power  of 
further  elongation.  The  lengthening  of  the  spiral  fibril, 
the  organ  of  muscular  movement  in  the  vorticellus,  belongs 
thus  to  the  living  state,  that  is,  to  the  continuance  of  nutri- 
tion and  exchange  of  matter.  As  soon  as  nutrition  has  been 
stopped  by  the  death  of  the  animal,  or  by  the  separation  of 
the  fibril  from  the  trophical  centre,  the  contractile  element 


90  CONTRACTILE  ELEMENTS. 

takes  and  keeps  the  form  naturally  belonging  to  its  structure, 
which  is  that  of  a  spiral  spring,  the  coils  of  which,  when  in 
the  state  of  repose,  are  as  near  as  possible  to  each  other. 

"  The  contraction  of  the  muscular  fibre  of  the  style  of  the 
vorticellus  corresponds  with  the  state  of  repose  of  the  spring, 
and  is  the  direct  consequence  of  its  elasticity ;  the  lengthen- 
ing of  the  fibre  is  the  result  of  the  forced  extension  of  the 
spring,  by  means  of  a  movement  connected  with  the  act  of 
nutrition,  and  acting  during  the  apparent  repose  of  the  con- 
tractile organ.  When  the  source  of  this  antagonistic  force 
is  dried  up,  the  elasticity,  by  bringing  the  muscle  back  to  its 
original  form,  produces  the  said  contraction.  .  .  .  The  ten- 
dency to  a  state  of  extreme  contraction  is  thus  an  inherent 
property  of  the  living  muscular  fibre,  a  necessary  result  of 
its  structure  and  of  its  elasticity.  During  life  this  tendency 
to  shorten  is  combated  by  an  extending  cause  which  pre- 
vails during  the  repose  of  the  muscle,  and  is  developed  in  the 
change  undergone  by  the  elements  of  nutrition,  increasing  as 
these  are  more  abundant,  diminishing  or  disappearing  in  their 
absence ;  and  it  may  be  momentarily  suspended  by  any  of  the 
excitants  of  muscular  contractility,  such  as  nervous  action, 
heat,  a  blow,  etc." 

In  another  series  of  investigations  Professor  Rouget,  ex- 
perimenting on  the  living  animal,  has  shown  that  any  thing 
which  is  an  obstacle  to  the  nutrition  of  the  fibre  causes  it  to 
contract.  By  tying  the  artery  of  a  limb,  and  constantly  in- 
creasing the  excitations  by  the  application  of  increasing  heat, 
he  found  that  he  obtained  always  the  same  results.  Accord- 
ing to  him,  the  effect  of  too  frequent  repetition  of  an  excita- 
tion, such  as  excessive  heat,  is  to  stop  the  progress  of  nutrition. 
In  both  these  cases  the  myograph  (see  p.  84)  has  shown  that 
the  contractions  of  the  fibrils,  becoming  more  frequent,  at 
length  follow  one  another  so  closely  that  there  is  no  longer 
any  interval  between  them,  and  the  muscle  then  enters  into 
the  state  of  tetanic  rigidity.  Thus :  "  the  tendency  to  shorten, 
which  is  the  result  of  the  peculiar  elasticity  of  the  muscular 
element,  is  permanent.  During  life  and  the  repose  of  the 
muscle  it  is  combated  by  a  tendency  to  lengthen,  the  energy 
of  which  is  in  proportion  to  the  activity  of  nutrition,  and 
expires  with  it.  Contraction  takes  place  at  the  moment 
when  the  equilibrium  between  these  two  opposite  tendencies 
is  broken  by  the  withdrawal  of  the  extending  power.  As 
the  coefficient  of  elasticity  varies  in  the  living  muscle  with 
the  different  states  of  repose,  contraction,  and  rigidity,  so 


STRIATED  MUSCLE.  .  91 

these  variations  modify  the  form  and  energy  of  the  contrac- 
tions. The  movement  by  which,  at  the  moment  when  con- 
traction takes  place,  the  Labor  of  muscular  extension  ceases, 
is  shown  under  the  form  of  an  increase  of  temperature.  The 
shortening  is  the  eiFect  of  the  peculiar  and  permanent  elas- 
ticity of  the  contractile  spiral  line ;  the  lengthening  is  pro- 
duced by  a  moving  cause  which  is  developed  in  the  act  of 
nutrition,  and  is  correlative  to  heat,  if  it  be  not  heat  itself."  ^ 

It  seems  certain,  as  we  have  already  said,  that  we  must 
place  the  change  of  form  of  the  muscle  in  the  general  class 
of  physiological  phenomena.  We  know  that  one  of  the 
essential  properties  of  the  globules  is  this  power  of  change 
of  form :  the  muscular  fibres  are  derived  from  the  globules, 
and  have  kept  this  property  in  a  very  striking  degree,  as  well 
as  the  other  properties  which  we  have  already  studied  (elas- 
ticity, electro-motor  power,  chemical  changes,  etc.)  The 
following  experiment  by  Kiihne  confirms  this  view  of  the 
subject,  by  which,  without  offering  any  theory  as  to  the  phe- 
nomenon, we  at  least  include  it  among  the  general  properties 
of  essentially  living  elements.  By  filling  a  fragment  of  the 
intestine  of  an  insect  with  protoplasm  of  the  myxocimetes 
(cryptogamous  plants,  composed  only  of  extremely  contrac- 
tile globules  of  pure  protoplasm),  he  formed  an  artificial 
muscular  fibre,  having  an  envelope  and  contents,  and  present- 
ing, under  the  action  of  excitants,  all  the  appearance  of  a  real 
muscular  fibre,  that  is  to  say,  passing  from  the  first  to  the 
second  form. 

As  with  the  globules,  however,  it  does  not  appear  that  the 
change  of  form  takes  place  at  once  in  the  whole  extent  of 
the  muscular  fibre.  If  we  examine  a  certain  portion  of  a 
fibre  with  the  microscope,  we  find  the  change  of  form  at  first 
local,  and  then  spreading  immediately,  like  a  wave,  along 
the  fibre.  This  experiment,  which  is  easily  made  on  the 
muscles  of  insects,  especially  on  the  long  slender  legs  of  the 
spider  (in  which  the  contraction  of  the  muscular  fibres  may 
be  observed  through  the  animal's  transparent  tissue),  con- 
firms what  we  have  already  quoted  from  Aeby  and  Marey 
(p.  88),  as  to  the  muscular  wave,  as  demonstrated  by  means 
of  the  myographical  pincers.^     In  it  we  make  use,  not  of  the 

'  Rouget,  "  Academie  des  Sciences,"  June,  1867. 

'  For  an  interesting,  as  well  as  instructive,  account  of  the 
changes  of  form  of  muscular  fibre  during  contraction,  as  seen  in  a 
muscle  attached  to  a  living  animal,  and  viewed  under  the  micro- 


92 


CONTRACTILE  ELEMENTS. 


change  in  length  of  the  muscle,  but  of  its  change  in  thick- 
ness, by  enclosing  it  in  a  kind  of  pincers,  one  of  the  movable 
branches  of  which  (myographical  pincers,  Marey)  operates 
on  a  registering  apparatus.  Of  course,  we  find  the  same 
simple  shocks,  or  elementary  contractions,  and  the  same  fusion 
of  these  shocks  in  physiological  tetanus,  as  with  the  former 
method,  but  the  process  is  more  practical,  and  may  be  made 
use  of,  for  instance,  to  register  the  contractions  of  the  biceps 
in  man. 


in.   Smooth  Muscles. 

The  smooth  muscvlar  fibres  (Fig.  21)  are  situated  chiefly 
in  the  coats  of  the  viscera  (intestine,  bladder,  uterus,  etc.), 
or  in  the   tubes  which   open   into   or   proceed   from   them 

(the  bronchus,  ureters, 
urethra,  bile  duct,  etc.). 
It  is  thus  difiicult  to  form 
a  distinct  group  of  this 
contractile  element,  for 
the  purpose  of  making  it 
a  special  study. 

Still,  by  studying  the 
smooth  muscles  as  we 
find  them  with  all  the 
normal  intricacies  of  their 
fibres,  we  are  easily  con- 
vinced that  these  ele- 
ments, like  the  striated 
fibre,  possess  the  property 
of  appearing  under  two 
difierent  forms,  which  we 

Smooth  muscles (o^f\ewaU of tiie bladder).  ^^^   f""^^    «^"  >^^    ^"^ 

second. 

The  smooth  muscle  appears  to  possess,  under  these  two 

forms,  the    same    properties    as   the    striated  muscle  under 

similar  forms,  as  well  in  regard  to  its  chemical  reactions,  as  to 


scope,  the  reader  is  referred  to  a  monograph  by  Professor 
Thomas  Dwight,  Jr.  (Boston  Nat.  Hist.  Soc.  Proceedings,  Nov. 
5,  1873.) 

*  A,  A  fasciculus,  from  which  proceed,  in  a,  o,  detached  cell  fibres,  b,  Repre- 
sents it  in  section.  B,  A  similar  fasciculus,  having  been  exposed  to  the  action 
of  acetic  acid  :  the  nuclei  appear  long  and  slender,  a  and  6,  as  above.  300  diam. 
(Virchow,  Pathologic  Cellulaire.) 


i 


SMOOTH  MUSCLES.  93 

the  electro-motor  force^  elasticity^  and  respiratory  exchanges 
(combustion).  But  what  distinguishes  the  smooth  muscle  from 
the  striated  muscle  is  that  in  the  former  the  passage  from 
the  first  to  the  second  form  is  made  with  extreme  slowness. 
After  the  excitation  which  irritates  the  fibre,  and  gives  rise 
to  its  change  of  form,  a  considerable  time  always  elapses 
before  the  change  occurs.  As  this  latent  excitation  lasts  a 
long  time,  so  the  contraction  which  follows  is  produced  very 
slowly,  continues  for  some  time  at  its  height,  and  then  grad- 
ually relaxes. 

Thus,  the  only  consequence  of  the  difference  in  structure 
of  the  smooth  muscles  is  that  they  yield  less  readily  to  the 
influence  of  irritaoits^  and  contract  more  slowly  than  the 
other  muscles.  They  also  pass  into  the  state  of  cadaveric 
rigidity  in  the  same  manner  as  the  striated  muscles.  A  state 
of  transition  between  the  striated  muscles  and  the  smooth 
muscles,  properly  so  called,  is  also  sometimes  observed.  This 
is  the  case,  up  to  a  certain  point,  with  the  muscular  tissue  of 
the  heart.     (See  p.  86.) 

On  resuming  a  series  of  investigations  as  to  the  compara- 
tive physiology  of  the  smooth  and  the  striated  muscles,  M. 
Leuros  and  M.  Onimus  arrived  at  the  following  conclusions : 
in  the  case  of  the  striated  muscles  both  the  contraction  and 
the  return  to  a  state  of  repose  are  rapid,  while  in  that  of  the 
smooth  nmscles  both  are  slow.  These  movements  are  always 
involuntary.  The  contraction  (physiological  tetanus)  of  the 
former  is  caused  by  a  series  of  shocks,  while  that  of  the  lat- 
ter conies  on  gradually,  without  oscillation.  The  peristaltic 
form  (see  intestine)  is  that  in  which  these  contractions  most 
frequently  appear.  The  motility  (excitability)  lasts  longest 
in  the  smooth  muscles  after  death.  In  the  striated  muscles 
electrical  excitation  of  the  motor  nerves  of  the  muscle  pro- 
duces more  effect  than  that  of  the  muscle  itself;  with  the 
smooth  element  the  reverse  is  the  case.  Finally,  if  the  two 
poles  of  an  induced  current  be  made  to  act  upon  the  smooth 
muscles,  by  placing  these  poles  at  a  certain  distance  from 
each  other,  we  find,  in  the  intestinal  tube,  for  instance,  that 
instead  of  the  whole  muscle  contracting,  those  parts  only 
contract  which  come  in  contact  with  the  poles ;  in  the  inter- 
mediate parts  there  is  no  contraction,  but  rather  relaxation. 
The  effect  produced  by  continuous  currents  is  still  more 
remarkable:  in  those  organs  which  have  peristaltic  move- 
ments (see  intestine ;  vaso-motors)  there  are  variations  cor- 
responding with  the  direction  of  the  current;    when   this 


94  CONTRACTILE  ELEMENTS. 

follows  the  direction  of  the  normal  peristaltic  contractions, 
relaxation  takes  place,  while  if  it  goes  in  a  contrary  direc- 
tion, contraction  is  produced. 

IV.    Contractile  Cells. 

The  different  properties  of  the  contractile  cells  resemble 
closely  those  which  we  have  studied  in  the  cells  in  general, 
especially  the  faculty  which  they  possess  of  changing  their 
form.  This  property  being  common  to  the  whole  mass  of 
protoplasm,  we  will  here,  after  speaking  of  the  muscle  prop- 
erly so-called,  mention  only  those  contractile  cells  which  are 
of  special  use  in  the  system,  on  account  of  their  contractility 
or  irritability.  Now  these  elements  are  to  be  found  scarcely 
anywhere  fully  developed,  except  in  the  arteries,  —  in  the 
smaller  arteries  especially.  Thus,  in  order  to  study  the  func- 
tions of  these  embryonic  muscular  forms,  we  must  examine 
the  small  vessels.     (See  circulation.) 

Among  the  movements  which  take  place  in  the  cells,  we 
must  also  mention  the  movements  of  the  vihratile  cells.  We 
shall  speak  of  these  in  reference  to  the  cylindrical  epitheli- 
ums which  are  found  to  have  this  ciliary  covering. 

V.   Adjuncts  of  the  Muscular  System. 

(Connective  Tissue,  Bones,  Tendons.) 

General  Mechanism  of  the  Muscles.  —  The  muscular 
fibre,  in  changing  its  form,  plays  an  important  part  in  the 
system  as  the  source  of  labor  and  of  movement.  For  this 
purpose  it  is  in  close  relation  with  other  organs,  and  exhibits 
two  difterent  tendencies,  acting  either  by  compression  or  by 
traction. 

In  the  former  case  {pressure)  the  muscular  elements  are 
arranged  in  the  form  of  handles  or  rings,  or  even  of  mem- 
branous pouches,  in  such  a  manner  as  to  compress  on  all 
sides  the  organs  which  they  enclose.  The  sphincters,  the 
muscular  tubes  (pharynx,  oesophagus),  and  the  heart,  as  well 
as  all  the  hollow  contractile  organs,  are  formed  according  to 
this  plan.  Nearly  all  the  muscles  of  the  organic  life  (smooth 
muscles)  exhibit  this  arrangement.  Their  function  is,  gen- 
erally, to  fiirther  the  passage  of  the  liquid,  or,  at  all  events, 
«q/5Jene^  matters,  into  the  interior  of  the  reservoirs  and  tubes 
of  which  they  form  the  walls,  and  thev  attain  their  end  by 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM, 


96 


means  of  the  unequal  pressure  which  they  produce  in  these 
reservoirs,  liquids  having  always  a  tendency  to  move  towards 
the  point  of  least  pressure.  (See  movements  of  the  stomach, 
of  the  intestine^  the  bladder,  icterus,  etc.) 

In  the  latter  case  the  muscular  fibre  is  inserted  in  the 
organs  which  it  is  intended  to  affect,  in  the  levers  which  it 
is  to  move  (bones)  by  the  medium  of  resisting  cords  (ten- 
dons). The  study  of  the  ligaments  belongs  to  that  of  the 
bones  (and  of  their  articulations) ;  the  study  of  the  aponeu- 
roses, to  that  of  the  tendons  and  the  muscles.    The  bones, 


CO' 


^^m^^^^&s&^^^y^^^^^ 


Fig.  22,  — Section  of  cartilage.* 

the  articular  cartilages,  the  ligaments,  the  tendons,  the 
aponeuroses,  thus  constitute  the  passive  organs  of  loco- 
motion. The  tissues  of  these  organs  are  so  associated  in 
histological  and  chemical  peculiarities,  that  they  have  been 
classed  together,  and  form  a  vast  family,  called  group  of 
connective  or  collage7ious  tissue.  The  tendons,  the  aponeu- 
roses, the  ligaments,  and  the  connective  substance  of  the 
organs  form  the  connective  or  cellular  tissue,  properly  so 
called. 

Connective   Tissue,  properly  so-called.  —  This  tissue  has 

*  c,  c,  Calcified  cartilage,    c',  (/,  The  calcareoxis  salts  are  just  beginning  to 
be  deposited.    />,  Pcfichondrium.  350  diam.  (Virchow,  "Cellular  Patholngv.") 


96  CONTRACTILE  ELEMENTS. 

the  closest  connection  With  the  muscular  element,  and  it  is 
this  which,  under  the  names  of  perimysium  and  enveloping 
aponeurosis,  unites  the  muscular  fibres  in  clusters  or  masses 
of  flesh,  so  as  to  admit  of  united  action  on  the  part  of  the 
contractile  elements ;  but  this  tissue  is  found  to  be  distrib- 
uted, not  only  in  the  muscles,  but  throughout  the  other 
organs :  it  was  formerly  called  cellular  tissue^  but  this  name 
is  inadequate,  for  it  expresses  only  a  general  disposition  of 
the  tissue,  by  means  of  which  it  is  easily  penetrated  by  the 
gjises  or  liquids  which  it  encloses  in  vacuoles  or  cells  (in  the 
macrographic  sense  of  the  word).  The  whole  body  may  be 
looked  upon  as  a  mass  of  connective  tissue,  or  of  one  of  its 
different  forms,  in  which  the  more  essentially  active  elements 
are  located.  Thus,  this  tissue  has  a  large  share  in  the  com- 
position of  the  nervous  centres,  prevailing  even  over  the 
nervous  tissue,  properly  so-called ;  and  the  knowledge  of  this 


Fig.  23.  —  Plasmatic  cells  of  the  cornea.* 

fact  has  lately  given  rise  to  entirely  new  views  as  to  the 
nature  of  diseases  of  the  cerebro-spinal  centres,  and  even  of 
the  nerves  in  general ;  as,  for  instance,  in  sciatic  neuralgia,  in 
which  the  pathological  change  is  generally  produced  in  the 
cellular  tissue  of  the  sciatic  nerve. 

The  connective  tissues  are  generally  rich  in  embryonic 
or  plasmatic  globules  (see  above,  p.  21),  or  their  derivatives : 
cartilaginous  cell,  bony  cell  (Figs.  24  and  25).  In  some 
places   these   globular   elements   appear   to  have  a  certain 

*  The  cornea  is  here  cut  parallel  to  its  surface.  The  star-shaped  corpuscles 
(embryonic  globules  or  plasmatic  cells)  ai-e  seen  flattened  out,  together  with  their 
anastomotic  prolongations  {His). 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.  97 

part  to  play,  as,  perhaps,  in  the  intestinal  villosities ;  and  here 
they  may  possibly  have  some  share  in  the  labor  of  absorp- 
tion ;  they  may,  besides,  by  being  filled  with  fat,  serve  as  a 
reservoir  for  this  substance,  as  in  the  pannicvlus  adiposus 
(subcutaneous  areolar  tissue)  of  a  child.  But  in  general  the 
globular  element  of  the  connective  tissue  takes  an  important 
part  only  in  pathological  phenomena,  when,  under  the  influ- 
ence of  a  more  or  less  direct  excitation,  it  proliferates  and  gives 
rise  to  the  pro<luction  of  pus  and  various  new  formations. 

Even  in  the  case  of  the  connective  tissues  which  have  the 
fewest  plasmatic  globules,  the  latter,  in  pathological  conditions, 
are  largely  developed.  When  the  aponeuroses,  for  instance, 
are  the  seat  of  suppurations,  we  find  them  transformed,  by 
proliferation  of  the  plasmatic  cells,  into  a  simple  mass  of  glob- 
ules. The  fewer  plasmatic  cells  there  are  in  a  connective  tis- 
sue, the  less  tendency  it  shows  to  change  under  the  influence 
of  pathological  causes ;  thus  the  tendons,  which  are  compar- 
atively poor  in  globular  elements,  are  slow  to  yield  to  the 
process  of  suppuration. 

The  globular  element  of  the  connective  tissue,  properly  so 
called,  as  well  as  of  its  derivatives  (collagenous  tissue,  bones, 
cartilage,  etc.),  being  important  only  in  pathology,  may 
be  almost  disregarded  in  physiology.  In  respect  to  the 
organs  which  are  formed  essentially  of  these  tissues,  we 
need,  therefore,  consider  only  some  of  their  physical  proper- 
ties and  mechanical  uses,  which  are  due  to  the  nature  of  the 
fundamental  substance  in  which  the  plasmatic  cells  are  im- 
bedded. 

These  physical  properties  are  very  different  from  each 
other,  and  are  sometimes  antagonistic,  though  found  in  very 
similar  forms  of  connective  tissue :  as,  for  instance,  the  rigid- 
ity of  the  bones,  and  the  elasticity  of  the  ligaments. 

The  J3ones.  —  The  bones  are  formed  of  lamellae,  enclosed 
one  within  another,  imbedded  in  calcareous  salts,  and  sur- 
round canals  containing  the  spinal  cord.  This  latter, 
formed  almost  entirely  of  embryonic  globules,  must  be  con- 
sidered as  living,  unless  the  globules  have  completely  passed 
into  the  state  of  fatty  degeneration.  In  a  purely  physiologi- 
cal point  of  view,  however,  the  bony  lamellae  show  scarcely 
any  trace  of  life.  It  is  true  that  the  bones  contain,  in  the 
calcareous  lamellae,  some  globular  elements  (such  as  bony 
corpuscles,  bony  cells)  which  are  similar  to  the  plasmatic  glob- 
ules (Fig.  24) ;  but  there  is  little  evidence  of  their  receiving 
nutrition,  and  they  are  of  importance  only  in  pathology.     It 

7 


98  CONTRACTILE  ELEMENTS. 

is  also  true  that  the  bones  grow ;  embryonic  globules  may  be 
seen,  in  their  circumference,  in  course 
of  proliferation,  some  bony  parts  dis- 
appearing, while  others  make  their 
appearance.  They  are  simply  chang- 
es of  form,  if  we  look  at  the  skeleton 
as  a  whole,  but  insignificant,  if  we 
consider  this  element  in  particular; 
and,  in  the  adult  stage,  the  bony 
lamellaB  have  only  physical  proper- 
ties. What  is  true  of  the  bones  is 
also  true  of  the  cartilages,  which 
are  really  bones,  only  less  rigid  and 

Fig.  24. -Histological  elements  more  elastic  than  what  are  usually 
or  the  bones.*  n    i  i       .1     .  "^ 

called  by  that  name. 

Tendons  and  Ligaments.  —  The  tendons  and  ligaments 
are  composed  essentially  of  wavy  or  undulated  fibres,  some- 
times interlaced  with  each  other,  but  which  give  no  appear- 
ance of  change  of  form,  so  that  we  may  almost  decline  to 
consider  them  as  living.  The  part  which  they  play  is  en- 
tirely mechanical,  and  belongs  to  their  powers  of  resistance 
and  elasticity.  We  find  the  latter  property  developed  in 
the  highest  degree  in  the  yellow  elastic  tissue,  which  is  a  non- 
collagenous  variety  of  connective  tissue ;  the  elastic  fibre  is 
still  more  undulated  than  the  cellular  fibre;  it  is  exceedingly 
curty  (Fig.  25,  d  and  c),  and,  when  stretched  out,  makes 
great  efforts  to  regain  its  original  foim :  the  yellow  or  elastic 
ligaments  also  serve  to  bring  the  different  parts  of  the  skele- 
ton back  into  their  normal  positions,  when  they  have  been 
disturbed  by  muscular  action,  whence  the  name  which  is 
sometimes  applied  to  them,  passive  muscles.  We  find  this 
elastic  element  always  at  work  in  the  arteries,  co-operating 
with,  or  in  opposition  to,  the  muscles ;  and  yet  the  result  of 
this  incessant  antagonism  is  the  uniform  circulation  of  the 
blood. 

In  general,  wherever  it  is  possible,  yellow  tissue  takes  the 
place  of  muscle.  This  element,  which  acts  like  a  spring,  and 
does  not  live  like  muscle  and  require  as  much  nourishment, 
whence  there  ensues  great  economy  to  the  system  (e.g.,  the 
cervical  ligaments  of  the  large  carnivora,  the  yellow  liga- 
ments of  the  vertebral  lamina,  the  yellow  ligaments  in  the 

*  Transverse  section  of  part  of  bone  enclosing  a  Haversian  canal  (n).  Bony 
corpuscles,  with  their  anastomosing  prolongations.  300  diam.  (Todd  and  Bow- 
man, "  rhysiological  Anatomy  of  Man."     Loudon,  18-45.     Vol.  1,  p.  109). 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.  99 

wing  of  birds,  in  the  wing  of  the  bat,  etc.).  These  parts, 
however,  do  not  require  to  be  frequently  renewed,  whence  the 
great  difference  between  the  connective  tissue  of  old  and 
young  people,  and  the  stiffness  in  motion  and  frequent  fract- 
ures which  we  observe  among  the  formen 


Fig.  25.  —Elements  of  connective  tissue:  connective  and  elastic  fibres.^ 

The  tendons  are,  in  a  mechanical  point  of  view,  only  soft 
and  flexible  processes  or  simply  appendnges.  Their  use  is  to 
enlarge  the  surface  of  the  bones,  so  as  to  admit  of  the  inser- 
tion of  a  greater  number  of  fibres.  Whenever  one  of  these 
processes  is  in  danger  of  beconiing  too  long,  and  by  its  con- 
sistency and  its  position  would  interfere  with  the  mechanism 
of  any  member,  it  beomes  a  tendon.  We  find  certain 
processes,  the  styloid  processes,  for  instance,  which  is  some- 

*  a,  Connective  ^bres^ '^hftviri^aj  pome^  fenibi^K)nk»globuleP.  6,  Ji^^stic  fibres, 
with  their  anastomoses ^ait^^ivisJp^ls.  c,  CivAy  elastic. fibred  (li|cu  )iorse-hair  in 
a  mattress),  d,  Nuclei  of  cells,  vith  niu'lecii/tabe^ry^iiltir  \\^^  jicctoral  muscle. 
320  diam.  (Todd^aix^  .B^iym^n, ,"  The  Physiological  Anatomy  o£''Man."  Lon- 
don, 1845,  p.  I^X  >  *x    '^   \  :  ^    "^   /;   '        \'^%^''  >  :    ^  ^  ^^    '  ^^    ^ 


100 


CONTRACTILE  ELEMENTS. 


times  bony,  and  sometimes  tendinous ;  while,  what  is  tendon 
in  man  becomes  bone  in  certain  animals.  In  reptiles,  for 
example,  the  linea  alba  becomes  a  bone,  and  the  intersections 
of  the  recti  muscles  are  represented  by  as  many  distinct 
bones.    In  birds  the  tendons  are  represented  in  certain  parts 

by  bony  stems,  placed  along  the 
extended  portions  of  the  principal 
bones."  The  existence  and  length 
of  the  tendons  depend  on  the  nat- 
ure and  extent  of  the  motion  to  be 
produced.  Whenever  this  is  of 
great  extent,  and  requires  great 
strength,  muscular  tissue  is  pre- 
dominant throughout  the  muscular 
apparatus,  and  is  directly  inserted 
into  the  bone.  Wherever  the 
movements  of  the  bony  parts  are 
of  small  extent,  find  require  only 
a  slight  shortening  of  the  muscle 
to  produce  them,  we  find  the 
fibres  of  this  muscle  short,  and 
ending  in  a  true  tendon. 

The  force  of  a  muscle  is  usually 
estimated  by  the  number  of  its 
fibres,  that  is  to  say,  by  its  thick- 
ness and  by  its  diameter  (see  p. 
87).  The  length  of  a  muscle,  on 
the  contrary,  corresponds  with  the 
degree  of  displacement  of  the  bones 
(compare  the  sartorius  and  the 
muscles  of  the  ball  of  the  thumb).  We  find  some  short 
muscles,  plnced  at  great  distances,  and  yet,  compared  with 
one  another,  possessing  slight  degree  of  movement.  In  such 
a  case  as  tliis,  a  tendon  takes  the  place  of  a  large  part  of  the 
muscle,  as  in  the  case  of  numerous  muscles  of  the  fore- 
arm, in  which  the  muscular  parts  are  short,  and  the  ten- 
dons very  long :  a  greater  length  of  muscular  fibre  would  be 
unnecessary  here  to  produce  such  a  slight  displacement  as 
the  flexion  of  the  hand  upon  the  forearm,  and  of  the  pha- 
langes against  each  other.  The  extensor  carpi  ulnaris 
muscle  appears  to  jbe  an'^eTPcep^iofi 'to  ithis  rule;  but,  in 
reality,  although  ijij  fleshy  ^^^f^rt  oceup^e^th^i  whole  length  of 

*  e,/,  9,  ^,  Embn'onic  globviles  of  conflectiyp  tis^ii9.'  'i^^tibn  of  these  ele- 
ments (pla'j5n>i1iic^o(a  libr«us  f^tS^M^  {Sd^wunn).     V  ^    «    ';_'■■. 


Pig.  26. 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM. 


101 


tlie  forearm,  its  muscular  fibres  are  very  short,  being  placed 
obliquely,  and  constituting  a  demi-penniform  muscle,  extend- 
ing li-om  the  ulna  to  the  tendon,  which  runs  the  whole  length 
of  the  forearm. 

Sometimes  the  sinewy  intersections,  which  are  placed 
along  the  path  of  a  muscle,  have  a  special  part  to  perform  : 
thus  the  intersections  of  the  rectus  of  the  abdomen  divide 
this  muscle  into  as  many  distinct  muscles,  thus  providing  for 
j)artial  contractions,  which  would  be  impossible  in  a  long 
muscle  made  entirely  in  one  piece:  the  same  may  be  said  of 
the  numerous  digastric  muscles  in  the  neck,  and  of  the  nape 
of  the  neck  (grand  complexus,  etc.). 

Mechanism  of  the  JBones,  considered  as  Levers.  —  In  the 
play  of  the  muscles,  of  the  tendons,  and  of  the  bones  we 
find  mechanical  apparatus  exactly  similar  to  the  three  kinds 
of  levers. 

The  lever  of  the  first  hind  is  to  be  often  met  with  in  the 
animal  economy.    In  the  case  of  man  we  might  call  it  the 


¥\g.  27. —  Showing  the  equilibrium 
of  tlie  head  upon  the  vertebral 
column.* 


Fig.  28.  — Diagram  of  the  foot  and 
ankle,  the  heel  being  raised  by  the 
tendon  of  Achilles  (Dalton). 


Standing  lever ;  for  it  is  in  the  equilibrium  of  the  erect  post- 
ure that  we  find  the  greatest  number  of  examples  of  it,  and 
it  is  very  rare  to  find  this  kind  used  for  movements  of  the 
body.  When  the  head  is  in  equilibrium  upon  the  vertebral 
column,  in  the  occipito-atloidean  joint  (Fig.  27)  it  represents 
a  lever  of  the  first  kind,  the  point  d'^appid  of  which  is  its 
junction  with  the  vertebral  column  (in  A).  The  resistance 
(weight  of  the  head)  lies  in  the  centre  of  gravity  of  the 


1 


*  Lever  of  tlie  first  class.  A,  Fixed  point.  R,  Resistance  (centre  of  gravity 
of  tlie  head).  1\  Force  (the  arrows  indicate  the  direction  in  which  the  force  and 
tile  resistance  act> 


102  CONTRACTILE  ELEMENTS, 

liead,  that  is  to  say,  above  and  a  little  in  front  of  the  centre 
of  motion  (in  R).  ThQ  power  is  represented  by  the  muscles 
of  the  nape  of  the  neck,  inserted  in  the  lower  half  of  the 
occipital  (in  P).  By  uniting  these  diiferent  points  we  obtain 
a  bent  lever  of  the  first  order,  which  can  be  easily  transformed 
into  a  direct  lever.  We  see  the  same  thing  exemplified  in 
the  preservation  of  the  equilibrium  of  the  trunk  upon  the 
lieads  of  the  two  femoral  bones :  the  coxo-femoral  joints 
form  the  leaning-point  of  a  lever  of  the  first  order,  in  which 
the  resistance  (centre  of  gravity  of  the  trunk)  is  placed  be- 
hind, and  the  power  (anterior  muscles  of  the  thigh)  is  placed 
before.  A  similar  lever  ia  found  in  the  articulation  of  the 
thigh  with  the  leg,  and  of  the  leg  with  the  foot  (in  the  move- 
ments of  equilibrium  to  maintain  the  erect  position). 

The  two  other  kinds  of  levers  are  to  be  principally  found, 
not  in  the  equilibrium  of  standing,  but  in  the  movements  of 
locomotion. 

The  lever  of  the  second  kind,  or  inter-resisting  lever,  in 
which  the  arm  of  the  power  is  longer  than  the  arm  of  the 
resistance,  and  in  which,  consequently,  speed  is  sacrificed  to 
strength,  is  found  in  man  only  under  two  circumstances^  — 
when  the  upper  part  of  the  trunk  is  raised  by  pushing  with 
the  palms  upon  a  resisting  plane,  and  when  the  whole  weight 
of  the  body  is  raised  by  standing  upon  the  points  of  the  toes, 
which  happens  at  each  step,  in  the  movement  of  walking, 


Fig.  29. —Example  of  a  lever  of  the  second  class,  as  shown  in  Fig.  28. 
(Dalton.) 

at  the  period  when  the  foot,  leaving  the  ground,  oscil- 
lates in  the  air,  and  places  itself  before  the  other.  In  this 
case  (Fig.  28)  the  point  d'appui  is  upon  the  axis  of  the 
transverse  cylinder,  formed  by  the  junction  of  the  series 
of  metacarpal  bones  with  the  phalanges.  The  power  is 
represented  by  the  muscles  of  the  tendo  Achillis,  and  its 
point  of  application  is  found  in  the  posterior  extremity  of 
the  OS  calcis.  The  resistance,  that  is  to  say,  the  weight  of 
the  body  transmitted  by  the  tibia,  lies  in  the  upper  facet 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.        103 

of  the  OS  calcis,  and  of  the  astragalus  (forming  a  single  bone 
in  movements  of  this  kind),  at  the  level  of  the  tibio-tarsal 
joint,  and,  consequently,  between  the  fixed  point  and  the 
point  of  application  of  the  power.  The  lever  arm  of  the 
power  is  thus  longer  than  the  arm  of  the  resistance ;  and, 
consequently,  the  power  to  raise  the  body,  displayed  by  the 
muscles  of  the  calf,  may  be  inferior  to  the  weight  of  the 
body  itself,  as  is  shown  us  by  the  law  of  levers  of  the  second 
kind  (Fig.  29). 

Tlie  lever  of  the  third  hind  (power  between  fulcrum  and 
weight)  is  the  most  common  ;  it  is  the  lever  of  locomotion  par 
excellence:  we  find  it  in  most  partial  or  complex  movements, 
and  especially  in  the  movements  of  flexion  and  extension.  We 
need  not  examine  the  shoulder  and  elbow  joints  in  the  act 
of  prehension,  in  order  to  establish  the  type  of  this  levei-,  for 
here  the  arm  of  the  power  is  always  shorter  than  that  of 
the  resistance,  so  that  the  energy  of  the  muscular  contrac- 
tion must  always  be  superior  to  the  resistance  to  be 
overcome.  Yet,  on  the  other  hand,  the  distance  traversed 
by  the  resisting  extremity  of  the  lever 
(the  hand,  for  example,  in  the  flexion 
of  the  forearm)  is  greater  than  that 
traversed  by  the  point  of  application 
of  the  force  (insertion  of  the  biceps 
in  the  upper  part  of  the  forearm) ; 
and  thus  what  is  lost  in  power  is 
gained  in  extent.  ^^'^\,  -magram  of  the 

Ine  workmg  oi  these  different  elbow,  as  a  lever  of  the 
levers  is  fiicilitated  by  the  disposi-  ^^^  '^^''•* 
tion  of  the  bones,  in  which  a  deep  cavity  is  hollowed  out 
(cancellated  texture),  filled  with  a  soft  and  almost  liquid 
matter  (marrow).  By  this  arrangement  the  weight  of  the 
bony  levers  is  diminished,  while  the  bone  affords  a  surface 
sufficiently  large  for  the  insertion  of  the  numerous  muscles 
by  which  it  is  moved.  The  substance  which  fills  these  cavi- 
ties is  the  lightest  in  the  whole  system,  —  fat  (marrow,  in  the 
adult).  Finally,  this  arrangement  of  the  bones  is  favorable 
to  the  part  which  they  play  as  supports,  for  mechanics  teach 
us  that  of  two  columns  of  the  same  height,  and  formed  of 
an  equal  quantity  of  matter,  one  being  solid  and  the  other 
hollow,  the  latter  will  be  the  stronger.     This  principle  ap- 

*  0,A,  Humerus.  A,  O',  Forearm.  M,  M',  The  biceps. — As  a  lever:  A. 
fixed  point ;  O',  point  of  application  of  the  resistance  (the  hand) ;  M',  point  of 
applicatiou  of  the  force. 


104  CONTRACTILE  ELEMENTS. 

pliea  to  tlie  hollow  columns  formed  by  the  bones  of  the 
different  members;  that  is  to  say,  given  an  equal  quan- 
tity of  bony  substance,  these  organs,  being  tilled  with  little 
canals  (canaliculi),  offer  greater  resistance  than  if  they  were 
solid,  and  thus  combine  strength  and  lightness. 

The  bones  are  not  merely  rigid  levers,  necessary  to  motion ; 
we  have  now  seen  that  they  serve  as  columns  or  supports  in 
standing,  intended  to  sustain  the  weight  of  the  body.  They 
form  also  a  more  or  less  complete  scaffolding  for  the  protec- 
tion of  certain  cavities,  such  as  the  ribs,  the  pelvis,  and  espe- 
cially the  skull,  which  supplies  an  incompressible  covering  to 
the  brain. 

The  Joints.  —  Tlie  parts  by  which  the  different  pieces  of 
the  skeleton  are  united  are  called  the  joints.  The  joints  are 
thus,  generally,  the  centres  of  motion ;  they  are  also  placed 
in  such  a  manner  as  to  avoid  friction  as  much  as  possible. 
The  cartilages,  which  cover  the  surface  of  the  joints,  are 
compressible  and  elastic,  and  thus  form  protecting  cushions 
which  serve  to  moderate  shocks,  to  diminish  friction,  and  to 
resist  pressure  in  the  different  movements  of  locomotion,  and 
in  the  equilibrium  of  the  erect  posture.  They  are  lubricated 
by  a  synovial  fluid,  which  is  a  ropy  and  unctuous  substance, 
and,  at  first  sight,  resembles  the  white  of  e^j^^j;,^  but  which,  by 
its  properties,  partakes  rather  of  the  nature  of  mucus,  prop- 
erly so  called.  Indeed,  as  is  the  case  with  all  mucus,  the 
synovial  fluid  is  the  result  of  the  liquefaction  of  an  epithe- 
lium which  lines  the  inner  surface  of  the  articulating  capsule. 
The  movements  and  friction  between  the  articulating  sur- 
faces have  great  influence  on  the  composition  of  the  synovia; 
when  the  animal  is  in  repose  this  fluid  is  very  watery,  less 
sticky  than  at  other  times,  and  contains  little  cellular  waste. 
After  long  and  active  exercise  it  becomes  thick  and  sticky, 
containing  a  larger  quantity  of  synovia,  or  mucine  (see 
physiology  of  the  mucous  sui-faces:  epitheliums),  and  of 
epithelial  waste  (Frerichs).  The  synovial  fluid  thus  pos- 
sesses great  power  of  cohesion,  and  adheres  firmly  to  any 
surface  which  it  bathes.  Strictly  speaking,  it  is  not  the  car- 
tilages, but  these  liquid  coats,  which  come  in  contact  with 
each  other,  so  that  scarcely  any  friction  ensues.  It  is  only 
in  some  cases  of  disease  that  the  synovial  fluid  disappears, 
and  consequent  attrition  occurring,  causes  rapid  atrophy 
and  destruction  of  the  adjacent  layers  of  cartilage  and 
bone. 

Around  the  joints,  beside  the  articulating  capsule  and  its 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.        105 

synovial  epithelium,  are  found  parts  which  are  formed  of 
resisting  fibrous  tissue,  called  articulating  ligaments.  Out- 
side the  joints  again,  and  around  the  muscles,  are  found 
other  fibrous  and  membraniform  apparatus,  called  aponeu- 
roses. The  object  of  these  two  apparatus  is  not  so  much,  as 
is  generally  supposed,  to  keep  the  articulating  surfaces  in 
contact,  as  to  limit  the  extent  of  the  movements  of  the 
joints.  The  ligaments  which  immediately  cover  the  joints 
act  as  resistance,  with  a  lever  arm  which  is  too  short,  and 
would  not  be  able  to  regulate  the  movements,  were  they  not 
aided  by  the  aponeuroses,  which  are  a  kind  of  ligament 
placed  farther  ofi",  and,  consequently,  more  powerful.  Thus, 
in  the  aponeurosis  of  the  thigh,  the  fascia  lata  is  only  a 
ligamentous  bridge  thrown  from  the  pelvis  to  the  leg,  thus 
belonging  to  the  coxo-femoral  and  knee  joint;  it  is  intended 
to  prevent  too  great  mobility  in  the  inferior  limb.  This 
fascia,  though  less  strong  than  the  articulating  ligaments,  ex- 
ercises in  this  way  a  much  more  important  influence,  because, 
being  placed  at  a  great  distance  from  the  centre  of  motion, 
it  acts  with  a  much  longer  lever  arm.  The  case  is  the  same 
with  the  cervical  aponeuroses,  which  are  only  ligaments, 
intended  to  prevent  the  too  great  inclination  of  the  head 
either  backward,  or  sideways:  here,  again,  these  are  only 
membranes,  weak  in  themselves,  but  which  become  powerful 
by  the  length  of  their  lever  arm. 

There  exist,  however,  a  certain  number  of  aponeuroses 
and  ligaments,  the  use  of  which  is  evidently  not  the  regular 
tion  of  the  movements  of  the  joints:  such  are  the  aponeu- 
roses of  investment,  which  prevent  any  deviation  in  the 
muscles  during  their  contraction.  Others,  as  the  annular 
ligament  of  the  wrist,  serve  as  pulleys  of  reflexion  for  the 
flexor  muscles.  Others  take  the  place  of  bones  for  the  inser- 
tion of  the  muscles :  such  are  the  interosseous  ligaments  of 
the  forearm  and  of  the  leg,  the  abdominal  linea  alba,  etc. 
On  the  other  hand,  the  sclerotic  coat,  an  essentially  fibrous 
membrane  in  the  eye,  is  intended  to  preserve  to  the  eye  its 
spherical  form,  which  form  is  necessary  for  the  preservation 
of  the  optical  properties  of  this  organ.  In  general,  the 
principal  use  of  the  fibrous  tissue  is  the  part  which  it  plays 
in  reference  to  the  joints. 

The  ligaments  serve  to  keep  the  bones  in  contact  only 
when  they  are  situated  between  two  bones,  as  in  the  case  of 
the  symphyses,  thus  uniting  two  parts  of  the  skeleton  which 


106  CONTRACTILE  ELEMENTS. 

have  little  motion.  But  in  the  movable  articulations  (diar- 
throses),  the  ligaments,  situated  principally  in  the  periphery, 
are  powerless  to  prevent  the  disturbance  of  the  articulating 
surface,  as  may  easily  be  seen  in  the  scapulo-humeral  and 
coxo-feraoral  articulations,  where  the  heads  of  the  bones 
may  be  considerably  displaced  from  the  socket,  in  spite  of 
the  perfection  of  the  ligamentous  system.  In  joints  of  this 
kind  it  is  simply  atmospheric  pressure  (Weber)  which  pro- 
duces the  adhesion  of  the  articulating  surface.  A  dead  body 
may  be  suspended,  the  lower  limbs  hanging  freely,  and  we 
may  then  remove  all  the  soft  parts,  skin  and  mnscle,  which 
surround  the  coxo-femoral  joint;  the  articulating  capsule 
may  then  be  cut,  and  the  limb  will  still  remain  suspended 
from  the  cotyloid  cavity :  an  additional  weight  may  even  be 
superimposed  without  destroying  the  adhesion ;  but  if,  by  an 
opening  made  in  the  bottom  of  the  cotyloid  cavity,  the  air 
is  allowed  to  penetrate  the  articulating  surface,  the  adhesion 
ceases  instantaneously,  and  the  head  of  the  femoral  bone 
-  quits  its  socket.  If  the  bones  be  then  replaced  and  the  air 
which  has  entered  expelled,  and  if  the  opening  previously 
made  be  stoj)ped  up  with  the  finger,  the  limb  will  again 
remain  suspended  as  long  as  the  air  is  kept  out  (experiment 
of  the  brothers  Weber).  It  is  thus  the  vacuum.,  or  the  close 
contact  of  surfaces,  which  allows  the  atmospheric  pressure  to 
act  as  a  counterpoise  to  the  limbs,  that  are  thus  supported 
without  any  aid  from  the  muscles. 

When,  by  stretching  the  fingers,  we  succeed  in  slightly 
separating  the  phalanges,  a  well-known  crackling  sound  is 
produced,  of  which  the  foregoing  study  supplies  an  explana- 
tion: the  stretching  of  the  joints  of  the  phalanges  overcomes 
the  pressure  of  the  atmosphere,  and  separates  the  articulat- 
ing surfaces  which  were  kept  in  contact  by  it ;  but,  at  the 
moment  of  separation,  the  soft  peripheric  parts  are  thrown 
by  the  same  pressure  into  the  space  between  the  two  bones. 
These  phenomena  are  very  sudden,  and  give  rise  to  sonorous 
vibrations,  whence  the  crackling  sound. 

The  preceding  remarks  on  the  mechanism  of  the  bones, 
of  the  muscles,  and  of  the  tendons,  help  us  to  understand 
the  dijBferent  kinds  of  labor  and  the  different  movements  of 
which  man  is  capable.  We  need  not  examine  the  action  of 
jumping,  of  climbing,  of  swimming,  etc.  We  will  only  con- 
sider, for  a  moment,  the  ordinary  walking  step,  the  brothers 
Weber  having  shown  that  in  this  mode  of  progression  each 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.        107 

of  the  two  legs  is  alternately  thrown  forward  by  an  oscilla^ 
tory  movement  exactly  similar  to  that  of  a  pendulum. 

Let  us  suppose  a  man  stopped  in  the  act  of  walking :  he 
has  just  completed  one  step,  and  stands  upon  his  two  legs, 
the  left,  for  instance,  being  placed  before,  and  the  right  be- 
hind. To  continue  liis  walk,  to  make  a  new  step,  what  hap^ 
pens  is  as  follows :  the  left  leg,  which  we  will  call  the  active 
leg^  is  placed  perpendicularly  upon  the  ground,  and  forms  the 
right  side  of  a  rectangular  triangle,  of  which  the  hypothe- 
nuse  is  formed  by  the  right  leg,  stretched  out  behind ;  the 
right  leg,  we  shall  see,  may  be  called  the  passive  leg.  The 
left  or  active  leg,  at  first  slightly  bent,  is  then  extended,  and 
carries  the  pelvis  forward  and  upward.  To  produce  this 
effect  the  heel  of  the  left  foot  is  raised  from  the  ground  by 
means  of  the  mechanism  which  we  explained  a  propos  of 
levers  of  the  second  kind,  and  the  limb  now  leans  only  upon 
the  extremity  of  the  metatarsus.  During  this  movement 
the  right  or  passive  leg,  being  forced  to  follow  the  forward 
movement  of  the  pelvis,  is  passively  detached  from  the 
ground,  and  makes  a  forward  movement,  like  a  pendulumj 
around  its  point  of  suspension  to  the  pelvis,  by  which  the 
right  foot  is  carried  as  far  before  the  active  foot  (the  left)  as 
it  was  previously  behind  it;  it  is  then  placed  upon  the 
ground,  and  the  movement,  by  which  the  active  leg  (the  left) 
throws  forward  the  pelvis,  being  continued  and  finished,  the 
right  foot  finds  itself  at  last  placed  perpendicularly  upon  the 
ground,  as  was  the  left  foot  at  the  beginning  of  the  step. 
The  step  which  we  have  been  considering  is  finished,  and  in 
the  new  one  which  follows  the  same  takes  place,  the  parts 
only  being  reversed :  the  right  leg  becomes  the  active  one, 
the  left  the  passive. 

In  short,  the  walking  step  may  be  represented  by  a  rec- 
tangular triangle  which  changes  its  position,  the  sides  mov- 
ing in  such  a  manner  that  the  one  which  represented  the 
right  side  at  the  beginning  of  the  step  (the  left  leg  in  the 
preceding  example)  passes  into  the  position  of  the  hypoth- 
enuse,  and  vice  versa.  The  leg  which,  from  the  right  side, 
passes  into  this  position  is  all  the  time  active^  while  the  leg 
which  passes  from  the  position  of  hypothenuse  into  that  of 
the  right  side  is  all  the  time  passive^  and  oscillates  in  the 
same  m,anner  as  a  pendulum.  In  order  to  oscillate  without 
touching  the  ground,  the  passive  leg  must  be  slightly  short- 
ened; this  takes  place  without  any  aid  from  the  muscles  of 


I 


108  CONTRACTILE  ELEMENTS. 

the  leg.  Indeed,  the  inferior  limb  represents,  in  oscillat- 
ing, a  double  pendulum  (the  thigh  on  one  side,  the  whole  of 
the  limb  on  the  other).  It  is  well  known  that  the  law  of 
oscillation  in  a  pendulum  is  that  a  pendulum  composed 
of  two  parts  united  by  a  joint  bends  sHghtly  in  the  joint  as 
soon  as  it  begins  to  swing. 

Some  physiologists,  however,  deny  that  the  leg  which  we 
have  called  passive  is  entirely  passive ;  they  maintain  that  it 
undergoes  a  slight  degree  of  contraction  of  the  flexors,  pre- 
cisely in  order  to  produce  the  flexion  necessary  to  the  oscil- 
latory movement.  Duchenne  (of  Boulogne)  draws,  from 
his  pathological  observations,  the  conclusion  that  the  oscil- 
latory motion  of  the  leg  would  be  impossible,  without  the 
contraction  of  the  flexors  of  the  thigh  upon  the  pelvis,  of 
the  flexors  of  the  leg  upon  the  thigh,  and  of  the  flexors  of 
the  foot  upon  the  leg.^  It  is  difficult  to  decide  on  this  sub- 
ject, for  some  authors  here  bring  in  the  question  oi  muscular 
tonicity^  and  that  of  thQ  predominance  of  the  flexors  over  the 
extensors.  On  these  questions  we  have  already  given  our 
opinion  (see  p.  72). 

Some  important  modifications  are  to  be  observed  in  the 
movements  made  in  walking,  according  as  they  take  place 
on  level  ground,  or  in  going  up  and  down  a  staircase,  for 
instance ;  and  these  have  been  carefully  analyzed  by  Marey 
("Journal  de  TAnatomie,"  1873).  We  cannot  pursue  the 
subject  further  here,  but  will  only  give  the  essential  features 
of  running,  as  mentioned  by  this  physiologist.  In  running 
there  is  no  double  support,  but,  on  the  contrary,  a  time  of 
suspension^  during  which  the  body  remains  for  a  moment 
lifted  above  the  ground,  one  foot  having  just  left  it,  and  the 
other  not  having  yet  touched  it.  The  length  of  this  time 
of  suspension  appears  absolutely  to  vary  very  little ;  but  if 
it  be  compared  with  the  length  of  a  step  in  running,  we  find 
that  the  relative  value  of  the  suspension  increases  with  the 
speed  of  the  running,  because,  as  this  increases,  the  length 
of  time  during  which  the  foot  remains  on  the  ground  is 
diminished.  What  is  most  remarkable,  however,  is  the 
means  by  which,  according  to  Marey,  this  interval  of  suspen- 
sion is  produced:  we  might  at  first  suppose  it  to  be  the 
effect  of  a  sort  of  leap,  by  which  the  body  is  thrown  upwards, 

'  Duchenne  (de  Boulogne),  *'  Physioloode  des  Mouvements." 
Paris,  1867,  p.  386. 


ADJUNCTS  OF  THE  MUSCULAR  SYSTEM.        109 

SO  as  to  describe  a  curve  in  the  air,  in  the  midst  of  which  it 
is  at  its  maximum  of  distance  from  the  ground.  This  is  not 
the  case ;  the  time  of  suspension  occurs  when  the  body  is  at 
the  least  distance  from  the  ground,  and  is  caused,  not  by  the 
body  being  raised  in  the  air,  but  by  the  legs  being  withdrawn 
from  the  ground^  during  their  flexion  (Marey), 


I 


PART   FOURTH. 
THE   BLOOD   AND   ITS   CIRCULATION. 

The  Blood. 

The  blood  is  a  liquid  which,  circulating  in  the  body  from 
the  periphery  to  the  centre  and  from  the  centre  to  the 
periphery,  diffuses  throughout  the  system  the  elements  ab- 
sorbed by  certain  globules  on  the  surface,  and  draws  the 
waste  parts  of  the  system  in  general  towards  other  globules 
on  the  surface,  whose  function  it  is  to  cast  them  off.  ^    In 

*  It  is  difficult  to  give  an  exact  definition  of  the  blood.  Physi- 
ologists consider  it  as  an  internal  medium.  ' '  The  name  of  medium 
is  given  to  those  conditions  which  surround  a  Uving  being,  and 
supply  it  with  all  that  is  needful  to  develop,  nourish,  and  exhibit 
the  life  by  which  it  is  animated.  .  .  .  We  must  distinguish  between 
the  cosmical  mediums  (air,  water,  food,  temperature,  light,  electri- 
city) and  the  internal  mediums:  the  former  surround  the  individual 
in  his  perfect  state ;  the  latter  belong  directly  to  the  anatomical  ele- 
ments of  which  he  is  composed."  (CI.  Bernard,  "  Proprietes  des 
Tissus  Vivants.")  But  this  general  definition  errs  by  being  too 
general;  it  is  easy  to  see  that  in  this  way  all  the  tissues  play  the 
part  of  medium  in  reference  to  each  other.  It  is  better,  therefore, 
to  consider  the  blood  as  a  tissue,  as  is  done  by  most  histologists  in 
these  days  (Frey,  Rouget) ,  and  to  define  it  as  a  cellular  tissue  con- 
sisting of  an  intercellular  Jluid  substance.  It  enters  thus  into  one  of 
the  four  great  classes  of  tissues  :  — 

1.  Cellular  tissue,  with  little  or  no  intercellular  substance, 
epitheliums  and  their  derivatives  (nails,  hair,  enamel,  crystalline 
substance) . 

2.  Cellular  tissues,  whose  substance  is  fundamentally  liquid 
(blood,  lymph,  chyle). 

3.  Cellular  tissues,  with  abundant  fundamental  substance,  such 
as  mucus,  hyaline,  or  fibrous  (cartilage  and  all  collagenous  or 
connective  tissues). 

4.  Tissue  formed  by  globules,  giving  rise  by  their  juxtaposition 
to  different  kinds  of  tubes  or  fibres  (muscles,  nerves,  vessels,  etc.). 


THE  BLOOD.  Ill 

this  system  of  constant  interchange  it  is  impossible  that  a 
perfect  balance  should  always  be  maintained.  The  blood 
has,  consequently,  no  fixed  normal  and  typical  composition. 
We  may  even,  in  any  given  movement,  distinguish  several 
different  kinds  of  blood,  especially  arterial  and  venous  blood. 
Any  analysis  of  the  blood  can  therefore  be  considered  only 
as  approximative. 

Quantity  of  the  Blood.  —  It  seems,  at  first,  easy  to  decide 
on  the  quantity  of  blood  contained  in  the  body,  but  this  also 
presents  great  practical  difliculties.  It  is  now  generally  ad- 
mitted that  the  human  system  contains  at  least  from  five  to 
six  litres  of  blood.  In  oixier  to  measure  this  fluid  mass,  the 
attempt  has  been  made  to  bleed  an  animal  white  (Herbst, 
Haidenhain) ;  but  a  certain  quantity  of  blood,  which  it  is 
impossible  to  measure,  will  always  remain  in  the  vessels. 

A  complete  injection  of  the  vascular  system,  for  the  pur- 
pose of  measuring  its  capacity,  has  been  found  equally 
unsatisfactory.  A  simpler,  and  at  the  same  time  more 
ingenious,  method  is  that  employed  by  Valentin.  It  con- 
sists in  calculating  the  quantity  of  blood  by  means  of  the 
dilution  which  it  undergoes  after  the  injection  of  a  definite 
quantity  of  water^  the  proportion  of  solid  and  liquid  which 
it  contained  at  first  being  known.  Let  us  suppose,  for  in- 
stance, that  the  blood  of  an  animal  contains,  at  a  given 
moment,  four  parts  of  liquid  to  one  of  solid,  this  proportion 
having  been  previously  settled  by  analyzing  the  blood  ob- 
tained by  blood-letting.  We  then  introduce  into  the  vascu- 
lar system  a  quantity  of  water  equal  to  that  of  the  blood 
which  has  been  withdrawn,  and  then  bleed  the  animal  again, 
by  doing  which  we  naturally  obtain  a  bloody  liquid,  more 
diluted  than  the  first.  Ifj  for  example,  the  first  bleeding 
produced  ten  grammes,  and,  after  the  injection  of  ten 
grammes  of  water,  the  second  bleeding  produces  blood  con- 
taining twice  as  much  water,  it  is  easy,  by  a  simple  computa- 
tion, to  calculate  the  quantity  of  blood  which  the  animal 
contained  at  first. 

There  are  great  objections  to  this  method  also,  on  account 
of  the  rapid  change  which  takes  place  in  the  blood,  and  in 
the  tissues  that  it  bathes,  even  in  the  short  interval  between 
the  two  bleedings:  the  blood  has,  in  fact,  a  tendency  to 
return  immediately  after  bleeding  to  its  original  condition, 
by  borrowing  this  fluid  substance  from  the  surrounding  tis- 
sues. 

A  still  better  method  is  that  of  washing^  as  employed  by 


112  THE  BLOOD  AND  ITS  CIRCULATION, 

Welcker.  The  head  of  an  animal  is  cut  off;  all  the  blood 
which  flows  is  collected,  and  its  coloring  power  measured. 
The  body  is  then  cut  in  pieces,  and,  being  thoroughly  washed, 
all  the  blood  is  withdrawn.  By  comparing  the  coloring 
power  of  the  bloody  water  thus  obtained  with  that  of  the 
blood  which  was  first  extracted,  it  is  easy  to  calculate  the 
proportion  of  blood  contained  in  the  water,  and  to  compute 
the  quantity  in  the  whole  body.  But  there  are  objections 
to  this  method  also,  among  which  we  need  only  mention 
that  by  washing  we  obtain  not  only  the  blood,  but  also  the 
coloring  matter  of  the  muscles,  of  the  marrow,  of  the  spongy 
bones,  of  the  spleen,  etc. ;  these  all  being  derived  from  that 
of  the  blood,  and  included  in  this  liquid,  would  give  it  more 
than  its  proper  value. 

It  is,  however,  generally  agreed,  as  the  result  of  experi- 
ments made  in  this  way,  that  the  total  weight  of  the  blood 
is  at  least  one-thirteenth  part  of  the  total  weight  of  the 
body,  which  would  give  for  man  five  kilogrammes  of  blood, 
his  mean  weight  being  sixty-five  kilogrammes. 

The  quantity  of  blood  varies  also  according  to  circumstan- 
ces :  the  state  of  fasting  or  digestion  has  the  greatest  effect 
in  influencing  the  quantity,  and  the  difference  in  these  states 
even  may  be  twofold.  This  has  been  directly  proved  by 
CI.  Bernard.  He  killed  two  dogs,  one  of  which  was  fasting, 
and  the  other  in  the  midst  of  the  process  of  digestion.  He 
proves  it  indirectly  by  showing  that,  to  kill  an  animal  in 
which  digestion  is  going  on,  a  dose  of  poison  is  required 
(strychnine,  for  instance)  double  that  which  would  suffice  to 
kill  the  same  animal  while  fasting.  It  is  true  we  must  re- 
member that  in  the  former  case,  not  only  the  system  in  gen- 
eral is  glutted  with  liquids,  but  the  anatomical  elements 
themselves  are  saturated,  and  thus  much  less  fitted  for  the 
absoi-ption  of  poison.  Collard  de  Martigny  mentions  a  still 
more  significant  fact,  which  is  this :  in  order  to  kill  a  rabbit 
in  its  ordinary  state  by  bleeding,  thirty  grammes  of  blood 
must  be  taken  from  it;  but,  after  a  three  days'  inanition,  the 
taking  of  seven  grammes  w^ill  produce  the  same  result.  We 
can  easily  see  how  important  this  fact  is  to  the  physician,  in 
regard  to  bleeding  a  patient  at  the  beginning  of  an  illness,  or 
after  several  days'  restricted  diet. 

Composition  of  the  Blood.  —  If  we  examine  the  blood 
from  an  anatomical  point  of  view  (as  a  tissue),  we  find  that 
it  is  composed  of  two  distinct  parts :  the  cruor^  which  com- 
prehends the  solid  part,  the  globules  ;  and  the  liquor^  which 


THE  BLOOD.  113 

comprehends  all  the  liquid  part  in  the  physiological  system. 
These  two  parts  are  in  equal  quantities,  and  we  may  thus 
define  the  blood  as  a  certain  mass  of  cruor,  floating  in  a 
quantity  of  liquor  of  equal  bulk. 

Yet  this  proportion  may  vary,  particularly  in  the  cases 
already  mentioned.  During  the  process  of  absorption  the  mass 
of  blood  may  be  doubled ;  it  is  the  liquor  especially  which  then 
increases,  and  this  increase  is  due  to  the  large  quantity  of 
lymph  which  is  poured  into  the  circulating  current.  (Colin 
collected  from  a  cow,  by  means  of  a  fistula  in  the  thoracic 
duct,  as  much  as  ninety-five  litres  of  lymph  in  twenty-four 
hours.)  After  copious  bleeding  also,  the  blood  has  a  tendency 
to  recover  its  former  bulk  by  borrowing  fluid  constituents 
from  the  adjacent  tissues ;  the  quantity  of  liquor  will  then 
be  increased,  the  process  being  much  slower  in  regard  to  the 
cruor.  We  know,  too,  that  death  generally  ensues  when 
half  the  blood  has  been  drained  away  by  hemorrhage,  or 
rather,  to  speak  correctly,  when  half  the  cruor  has  been 
withdrawn,  the  importance  of  which  fact  is  evident  in  the 
case  of  successive  bleedings ;  because  the  liquid  part  of  the 
blood,  and  not  the  globules,  has  had  time  to  be  re-formed. 

Cruor.  —  This  is  the  solid  part  of  the  blood,  and  is  formed 
entirely  of  globules,  floating  in  liquid;  the  blood  globules  are 
of  two  kinds,  red  and  white. 

a.  The  white  globules  of  the  bloody  better  named  colorless 
globules  (Leucocytes,  Robin),  are  a  little  larger  than  the  red 
(from  eight  to  nine  thousandths  of  a  millimetre  in  diameter), 
but  much  less  numerous  (there  is,  in  general,  one  white  to  three 
hundred  red  globules)  ;they  are  spherical  in  shape,  and  sim- 
ilar in  every  respect  to  the  lymph  globules  which  are  found 
in  the  lymphatic  glands:  they  originate,  in  fact,  in  these 
glands,  and  are  subsequently  detached  from  them,  and  drawn 
by  the  lymph  into  the  thoracic  duct,  whence  they  spread, 
with  the  lymph,  throughout  the  blood.  These  globules  are 
round,  having  nuclei,  and  a  slightly  granular  surface  (Fig. 
31).  When  examined  in  the  liquor  of  the  blood,  with  a 
magnifying  power  of  from  200  to  300  diam.,  they  seem  to 
have  a  granular  appearance  and  are  irregular  in  shape,  their 
color  being  a  peculiar  silvery  white.  Under  these  circum- 
stances it  is  impossible  to  distinguish  any  other  details  of 
their  structure ;  but,  on  the  addition  of  water,  we  find  that 
these  elements  increase  in  size,  their  outline  becomes  smooth, 
and  a  nucleus  appears,  sometimes  double  or  multiple ;  the 
addition  of  acetic  acid  renders  these  features  still  more  dis- 


114  THE  BLOOD  AND  ITS   CIRCULATION. 

tinct,  and  sometimes  divides  the  nucleus  in  several  parts,  or 
makes  two  or  three  nuclei  appear  at  once  in  one  globule 

r.ff^A  -J^®  ^K*      pose  probably  is  to  form  the  red 

My'P®  W®   globules,  and  we    find,  between 

^^  ®^  (g)  @)@  ^i    these  two  kinds  of  globules  some 

#^  ^^  intermediate  elements  in  respect 

*  ^  to  color  and  form.  Under  cer- 
Fig.si.-white  globules  of  the  blood  tain  circumstances,  and  particu- 

(Leucocyt^,-  Bobin  ♦  i      i       •        v  V  ^i        i^  i? 

larly  in  diseases  of  the  liver,  of 
the  spleen,  and  of  the  lymphatic  glands,  these  white  globules 
increase  in  number  until  they  form  one-third  or  one-half  of 
the  globular  portion  of  the  blood,  which  then  appears  of  a 
lighter  color  (whence  the  name  oi'leucemie  or  leucocythemia). 
This  accumulation  of  white  globules  appears  to  arise  from 
some  obstacle  to  their  transformation  into  the  red  globules, 
or  from  their  being  produced  in  greater  numbers  by  the 
spleen  (splenetic  leucocythemia),  or  by  the  lymphatic  glands 
(lymphatic  leucocythemia).  But  even  in  the  physiological 
condition  we  find  considerable  variation  in  the  numerical 
proportion  of  the  white  globules  to  the  re^d :  thus  the  former 
diminish  under  the  influence  of  abstinence^  and  in  the  case 
of  persons  advanced  in  years ;  on  the  other  hand,  they  in- 
crease after  eating,  after  hemorrhage,  in  children,  and  in 
women  during  pregnancy ;  this  increase,  especially  that  after 
eating,  constitutes  what  is  called  physiological  leucocytosis. 
The  white  globules  are,  finally,  more  abundant  in  certain 
pai-ts  of  the  vascular  system,  such  as  the  veins  of  the  liver 
and  of  the  spleen ;  and  this  is  an  important  fact  in  the  study 
of  the  physiology  of  these  organs. 

h.  The  red  globules  (Jiematies^  Gruithuisen,  Robin),  form  the 
principal  part  of  the  cruor  (three  hundred  red  to  one  white). 
It  has  been  calculated  that  a  litre  of  blood  contains  five  bil- 
lions of  these,  which  makes  their  entire  number  twenty-five 
billions.  The  red  globule  is  thus  the  most  largely  diffused 
of  the  elements  of  the  system ;  and,  since  nearly  half  the 
blood  is  composed  of  it,  it  forms  the  principal  organ  of  the 
whole  body.  The  process  most  commonly  employed  to 
determine  the  number  of  globules  in  any  given  quantity  of 
blood  is  that  invented  by  Vierordt,  and  improved  by  Potain, 

*  A,  Fresh  white  globules,  a.  White  globule  in  its  natural  fluid,  b,  White 
globule  in  water.  B,  White  globules  treated  by  acetic  acid,  a,  c,  Non-nucleated 
white  globule,  b,  Division  of  the  nucleus,  rf,  Division  (more  advanced)  of  the 
nucleus ;  jT,  h,  t,  A;,  still  more  advanced.    (Virchow,  "  Pathologic  Cellulaire.") 


.     THE  BLOOD.  115 

and  more  recently  by  M.  Malassez.  It  consists  in  diluting 
with  a  certain  quantity  in  distilled  water,  collecting  a  portion 
of  this  mixture  in  a  capillary  tube,  and  deciding,  by  the  aid 
of  a  graduated  micrometer,  or  simply  by  that  of  the  micro- 
scope, what  is  the  quantity  contained  in  a  portion  of  the  tube. 

The  red  globules.,  or,  properly,  blood  globides^  are  small 
disks,  excavated  on  both  surfaces,  and  thicker  at  the  edges 
(Fig.  32)  ;  their  diameter  is  y^^  of  a  millimetre,  and  their 
thickness  is  ^J^. 

Considered  histologically,  the  red  globules  are  small  mnsses 

of  protoplasm,  combined 'with  certain  chemical  compositions 

(see,  farther  on,  globuline^  hematine.,  etc.) ;         ^t       e 

seen  in  section,  these  elements  appear  in        ©0Q15   g 

the  form  of  a  biscuit,  narrow  in  the  mid-     ©   0881  /,®®^ 

die,  and  widening  at  the  two  extremities  *     *i<^^f 

(Fig.  32,  c).     In  front,  they  appear  as  disks  9 

of  a  yellowish  color,  darker  at  the  edges,  pj^  33, 

more  transparent  towards  the  centre  (Fiff.  Blood  globules  of  an 
f»,v       X        mi  J*  ^"      1.  1    •  adult  man.* 

32,  a).     I  here  are  no  distmct  nuclei    or 

envelope,  but  a  very  thin  limiting  layer,  which  seems  to  in- 
dicate the  presence  of  an  enveloping  membrane,  or,  at  least, 
of  a  sort  of  girdle,  more  condensed  than  the  globules,  and 
having  a  different  composition.  The  absence  of  membrane 
has  been  thought  to  be  demonstrated  by  the  deformities 
which  these  globules  undergo  when  subjected  to  a  tempera- 
ture of  from  40^^  to  45^*  (Ranvier),  or  to  the  action  of  car- 
bonate of  potash  (Dujardin),  Under  these  circumstances 
they  become  flatter,  and  change  their  shape  into  that  of  a 
number  of  caps  or  cups,  whose  edges  have  been  recently  and 
regularly  united  to  each  other.  We  observe  the  same  phe- 
nomena, however,  under  like  circumstances,  in  the  bodies  of 
the  infusoria  (Rouget),  which  certainly  have  a  covering,  or, 
at  least,  a  cortical  layer  {hautschicht  of  the  Germans).  Fi- 
nally, by  the  action  of  picric  or  chromic  acid,  we  discover  a 
distinct  membrane ;  this  is  still  more  visible  in  the  batrachi- 
ans,  in  which,  under  the  influence  of  hibernation,  colorless  vacu- 
oles, or  fragments  of  the  coloring  matter,  radiating  like  the 
spokes  of  a  wheel,  are  formed  in  the  blood  globules  (Rouget). 

*  a,  Ordinary  red  globule,  having  the  form  of  a  disk,  h,  White  globule. 
c,  Red  globules,  seen  from  the  side,  being  placed  upon  their  edge,  d,  Red  glob- 
ules, piled  one  upon  the  other,  like  coins,  e,  Red  globules,  with  shrunken  edges, 
a  part  of  the  contents  of  which  has  been  lost  by  exosmosis,  whence  their  shrunken 
or  crenated  appearance.  /,  Red  globules  (the  edges  being  uneven,  and  the  sur- 
face exhibiting  a  swelling  resembling  a  nucleus);  g^  still  more  shrivelled; 
A,  final  degree  of  crenation.    280  diam.    (Virchow.) 


116  TEE  BLOOD  AND  ITS  CIRCULATION. 

The  red  globules  change  very  easily:  the  slightest  evapo- 
ration, the  slightest  concentration  of  the  liquid  in  which  they 
float,  gives  them,  by  exosmosis,  a  shrivelled  form,  indented 
or  crenated  (Fig;  32)  at  the  edges,  and  thus,  when  seen  in 
fi-ont,  they  present  a  false  impression  of  an  apparent  nucleus 
(Fig.  32,/). 

The  form,  the  size,  and  even  the  structure  of  the  red  glob- 
ules is  not  the  same  in  different  animals,  or  even  in  the  same 
animal  at  different  stages  of  development.  The  globules  of 
the  human  fcetus  are  distinguished  from  those  of  the  adult 
by  the  existence  of  a  nucleus,  and  it  is  only  towards  the 
second  half  of  the  intra-uterine  existence  that  they  lose  this 
feature.  The  blood  globules  of  the  adult  mammalia  are 
similar  in  form  to  those  of  man,  but  differ  in  size :  those  of 
the  guinea-pig,  of  the  goat,  of  the  sheep,  of  the  horse,  and 
of  the  rabbit  are  smaller ;  those  of  the  dog,  about  equal  in 
size ;  those  of  the  elephant,  much  larger.  The  camel  and 
llama,  alone  among  the  mammifera,  have  globules  elliptical 
in  shape,  and  always  without  nucleus.  In  birds  the  globules 
are  larger  than  in  the  mammifera,  elliptical  and  biconvex, 
and  present  some  traces  of  a  nucleus.  The  globules  of  rep- 
tiles and  of  the  amphibious  animals  (Fig.  33)  are  large, 
elliptical,  and  biconvex,  with  a  visible  nucleus,  as  is  the  case 
generally  with  fishes.  The  following  figures  will  be  suflicient 
to  give  an  idea  of  the  differences  in  size :  in  man  the  red 
globules  measure  y^^  of  a  millimetre,  and  in  the  proteus  ^. 
The  presence  of  colored  globules  in  the  blood  is  usually 
considered  a  distinguishing  feature  of  vertebrate  animals. 
Rouget  has,  however,  long  since  pointed 
out  the  existence  of  similar  elements 
in  the  invertebrate:  in  this  case  they 
are  generally  without  any  covering, 
granulated^  and  supplied  with  a  coloring 
matter  (hematine,  see  farther  on),  which, 
instead  of  being  uniformly  diffused,  is 
present  in  small  distinct  quantities.  The 
^'to?B~hfoT%onJ,  globules  of  the  sipunculus,  however,  are 
J' Atlas  du  ^Cours  de  composed  of  a  thick,  elastic  envelope, 
icroscopie,  ig.  ).  ^.^j^  ^  double  outUne,  enclosing  a  pink- 
ish, homogeneous  substance,  which  is  very  refrangent. 

In  a  physiological  point  of  view  the  red  globules  are 
remarkable  for  their  elasticity :  they  are  slightly  and  perfectly 
elastic ;  they  change  their  shape  on  the  slightest  pressure, 
but  return  easily  to  their  original  form.     In  examining  the 


THE  BLOOD.  117 

circulation  of  the  blood  with  a  microscope  (in  the  mesentery 
of  the  frog,  for  instance),  we  sometimes  see  the  globules 
bend  in  two,  or  mount,  as  if  on  horseback,  the  spur  thrown 
out  by  the  bifurcation  of  a  vessel.  What  is  still  more  re- 
markable, they  may,  under  certain  circumstances,  alter  their 
shape  and  size,  by  a  sort  of  contractility  which  is  shown  par- 
ticularly when  they  are  subjected  to  the  influence  of  oxygen 
gas  or  of  carbonic  acid ;  the  result  of  this  change  of  form  is 
a  change  of  color.  When  the  globule  is  flattened  and  hol- 
lowed out  by  the  influence  of  oxygen,  it  appears  brighter  and 
redder  (arterial  blood)  ;  when  it  is  gathered,  as  it  were,  into 
a  ball,  under  the  influence  of  carbonic  acid,  it  becomes  darker 
(dark  color  of  the  venous  blood). 

In  a  chemical  point  of  view  we  notice  the  interesting  facts 
that  the  red  globules  contain,  as  mineral  substances,  different 
salts  from  those  of  the  liquor;  that  is  to  say,  principally 
phosphates  and  salts  of  potash,  while  the  liquor  contains 
principally  carbonates  and  salts  of  soda.  We  have  already 
mentioned,  as  one  of  the  general  properties  of  the  living 
globule  (see  part  first,  p.  7),  its  power  of  maintaining  the 
original  composition,  in  spite  of  the  laws  of  osmosis  and 
of  diffusion.  From  the  fact  of  these  ingredients  being  found 
in  the  blood  globule  we  may  infer  that  salts  of  potash  would 
be  useful,  instead  of  salts  of  soda,  when  our  object  is  to 
restore  this  particular  element  of  the  bloOd  (in  aglobulia,  a 
disease  where  the  number  of  globules  is  diminished). 

Water  in  the  blood  globule  is  contained  in  the  proportion  of 
two-thirds,  a  proportion  inferior  to  that  found  in  the  globular 
elements  generally  (four-fift^hs).  The  most  noticeable  element 


Fig.  34.  —  Crystals  of  hsemln.* 


1 


of  the  blood  globule  is  an  organic  substance  of  the  nature  of 
albumen,  which  possesses  the  property  of  crystallization.  It 
is  called  hemoglobin,  and  is  composed  of  globulin  (a  com- 
position  resembling   casein   rather   than   albumen)    and   of 


*  Obtained  from  the  blood  artificially,  by  the  action  of  cooking  salt  and 
acetic  acid  (chlorate  of  hcmatine).    300  diam.     (Virchow.) 


118  THE  BLOOD  AND  ITS   CIRCULATION. 

hematosine  (a  proteid  substance,  containing  the  coloring 
matter  of  the  globule).  By  injuring  or  destroying  the  glob- 
ules we  obtflin  first  a  solution  of  a  bright  red,  which  shortly 
deposits  crystals  of  different  forms,  varying  in  the  case  of 
different  animals.  These  crystals  are  red,  generally  irregular 
in  shape,  and  easily  destroyed.  They  are  crystals  of  hemo- 
glohin  or  hematocrystalUn.  Under  the  influence  of  different 
reagents  this  substance  develops  new  forms,  such  as  haemin 
and  haematoidine^  which  crystallize  into  more  regular  forms 
and  with  darker  colors  (Fig.  34,  haemin  crystals).  Hematin 
contains  7  per  cent  of  iron,  and  as  there  are  about  100 
grammes  of  hematin  in  the  entire  mass  of  the  blood,  the 
quantity  of  iron  contained  in  the  body  would  appear  to  be 
about  7  or  8  grammes. 

Hemoglobuline  becomes  crystallized  sometimes  sponta- 
neously, but  more  particularly  when  under  the  influence  of 
certain  reactions  or  of  certain  physical  actions,  such  as  re- 
peated freezing,  followed  by  melting.  In  man  it  is  then 
precipitated  under  the  form  of  prismatic  crystals.  In  the 
mouse  and  the  guinea-pig  the  crystals  are  tetraedic,  and 
hexagonal,  also,  in  the  case  of  the  squirrel. 

Hematin.,  on  the  contrary  (or  hematosine),  which  is  the 
coloring  matter  of  the  blood,  properly  so  called  {heinoglobin^ 
without  the  globulin').,  forms  quite  spontaneously  in  effusions 
of  blood  in  the  tissues,  and  in  blood  kept  for  a  long  time  in 
a  vessel :  it  is  always  amorphous,  and  appears  as  granulations 
of  a  deep-red  color. 

By  combining  hematine  with  an  acid,  hydrochloric  acid, 
.for  instance,  we  obtain  a  new  body,  haemin  (or  chlorate  of 
hematine  (Fig.  34),  the  crystals  of  which  appear  in  the  shape 
of  rhomboid  plates,  flattened  at  the  corners,  and  of  a  deep 
brown  color.  The  crystals  thus  obtained  are  found  only  in 
the  blood. 

Hematoidine.,  finally,  is  derived  from  hematine,  and  is  pro- 
duced spontaneously  in  the  system,  particularly  in  old  hem- 
orrhagic spots,  and  generally  in  all  effusions  of  blood. 

This  substance,  which  appears  in  the  form  of  small  rhom- 
boid and  oblique  crystals,  is  identfcal  with  the  coloring 
matter  of  the  bile.  Chemically  considered,  hematoidine  is 
not  identical  with  hematine ;  the  difference  is  one  part  less 
of  iron  and  one  more  of  water. 

These  coloring  matters  of  the  blood,  particularly  the  hem- 
ato-crystalline,  have  been,  during  the  last  few  years,  the  object 
of  very  interesting  researches,  by  means  of  their  spectral 


THE  BLOOD. 


119 


analysis.  Hoppe  Seyler  (1862)  and  Valentin,  in  Grermany; 
Stokes  and  Sorby,  in  England ;  Bert,  Claude  Bernard,  Be- 
noit,^  and  Furaouze,^  in  France,  have,  by  applying  to  the 
study  of  the  blood  the  means  of  analysis  discovered  by 
KirchofF  and  Bunsen,  shown  that  when  a  large  solution  of 
arterial  blood  is  examined  through  a  prism  (spectroscope) 
by  the  light  of  the  sun  or  of  a  lamp,  we  find,  instead  of  the 


Red. 


Yellow. 


Green. 


Blue. 


Violet 


A.     B     C  D 


E  ¥ 


u 


Fig.  36.  — Absorption  of  certain  parts  of  the  spectrum  by  solutions  of  blood.* 

ordinary  luminous  spectrum,  one  crossed  by  broad  dark 
bands  (placed  as  in  Fig.-  35)  ;  this  is  called  the  absorption 
spectrum  of  the  Mood:  it  is  essentially  characterized  by 
two  dark  bands  in  the  yellow  and  green,  and  also  by  the 
almost  entire  extinction  of  the  most  refrangible  rays,  begin- 
ning at  the  blue  or  the  indigo  (Fig.  35,  C). 

It  is  remarkable  that  the  venous  blood,  and  that  which  has 

*  R.  Benoit,  "  Etudes  Spectroscopiques  sur  le  Sang."  These, 
Montpelier,  1869. 

'  Fumouze,  "  Les  Spectres  d' Absorption  du  Sang."  Paris, 
1871,  in  4to. 

*  A,  Fraiinhof  er  lines.  B,  Oxygenated  arterial  blood  (two  bands  of  absorption 
between  the  lines  D  and  E  of  Fraiinhof  er,  that  is,  in  the  yellow  of  the  spectrum). 

C,  Arterial  blood  in  a  more  concentrated  state  of  solution  (absorption  of  all 
the  rays  beginning  at  F,  that  is,  the  blue). 

Dj  Solution  still  more  concentrated.  E,  Venous  blood,  reduced  blood;  ab- 
sorption band  near  the  line  D  of  Fraunhofer  (that  is,  in  the  yellow).  (Paul 
Bert.) 


120  THE  BLOOD  AND  ITS  CIRCULATION. 

lost  its  oxygen,  as  well  as  solutions  of  hemoglobiiline  which 
have  been  deoxidized  by  any  reducing  agent,  present  a  differ- 
ent spectrum :  the  interval  which  separates  the  two  bands  is 
darkened,  or,  in  other  words,  the  two  black  bands  fuse  into 
one  {reduction  band  of  Stokes)  (Fig.  35,  E).  At  the  same 
time  the  shading  which  covers  the  most  refrangible  part  is 
withdrawn  towards  the  violet,  so  that  there  is  more  transpa- 
rency to  the  blue  rays. 

There  is  thus  a  spectrum  of  oxygenated  blood  and  of 
deoxidized  blood,  of  oxygenated  hemoglobuline  and  of 
reduced  hemoglobuline. 

Claude  Bernard  and  Hoppe  Seyler  demonstrated,  at  about 
the  same  time,  that  oxide  of  carbon  drives  the  oxygen  from 
the  blood  and  takes  its  place,  entering  into  combination  with 
hemoglobuline.  This  combination  gives  a  spectrum  (spec- 
trum of  oxycarbonated  blood,  very  similar  to  that  of  the 
oxygenated  blood,  with  the  exception  of  the  two  black 
bands  being  slightly  displaced  towards  the  right.  The  prin 
cipal  feature  in  this  spectrum  is  that  the  action  of  reduc- 
ing elements  produces  no  change  in  it ;  in  other  words,  the 
spectrum  of  oxycarbonated  hemoglobuline  does  not  furnish, 
like  that  of  oxygenated  hemoglobuline,  Stokes's  band  of 
reduction.  The  importance  of  these  discoveries  and  of  their 
aj)plication  is  evident  in  the  case,  for  instance,  of  a  person 
suffocated  either  by  the  fumes  of  charcoal  or  the  oxide  of 
carbon.  It  is  also  important  to  notice  that  these  distinguish- 
ing bands  can  be  obtained  by  washing  with  water  old  blood- 
stains upon  iron,  wood,  linen,  etc.,  even  where  the  blood  is 
already  decomposed  and  putrid.  Valentin  has  proved  satis- 
factorily the  presence  of  blood  upon  a  board  taken  from  a 
dissecting  table,  which  had  lain  unused  in  a  damp  place  for 
three  years,  and  also  upon  a  rusty  butcher's  hook,  which  had 
been  long  tkrown  aside.  Numerous  attempts  have  been 
made  in  vain  (Kitter)  to  discover  any  coloring  matter,  of 
which  the  spectrum  could  possibly  be  mistaken  for  that  of 
the  blood,  or  which  could,  by  means  of  the  agents  of  reduc- 
tion, show  any  thing  analogous  to  the  ba7id  of  Stokes. 

This  method  of  research  is  beyond  almost  every  thing  that 
could  be  desired  on  the  score  of  minuteness ;  for  Valentin 
has  discovered  indisputable  traces  of  the  blood  spectrum  in 
a  solution  containing  only  seven-thousandths  of  blood  in  a 
thin  layer  of  fifteen  millimetres. 

By  successive  study  of  the  spectrum  of  oxygenated  and 
deoxygenated  blood,  of  oxygenated  and  reduced  hemoglob- 


THE  BLOOD.  121 

nline,  which  spectra  can  be  produced  by  alternately  taking 
away  and  restoring  the  oxygen  of  the  solution  of  blood,  we 
bring  a  new  element  to  the  explanation  of  the  difference  of 
color  in  arterial  and  venous  blood.  This  difference  is  not 
due  only  to  changes  in  form  in  the  globules,  for  these  changes 
in  color,  which  correspond  with  the  differences  in  the  spec- 
trum of  arterial  and  venous  blood,  are,  like  these,  tlie  result 
of  alternations  of  oxidation  and  of  reduction  of  the  hemo- 
globuline,  so  that  the  arterial  and  venous  blood  represent  the 
two  states  of  oxidation  and  reduction  of  the  coloring  matter 
of  the  blood. 

The  physiological  function  of  the  red  globules  consists 
entirely  in  the  absorption  of  oxygen  which  they  then  impart 
to  the  tissues.  They  are  the  receptacles,  the  condensing 
apparatus  of  this  gas,  similar,  so  to  speak,  to  coal  and  to  the 
sponge  of  platina.  In  traversing  the  pulmonary  capillaries 
they  borrow  the  oxygen  from  the  outer  air,  and  then  carry  it 
to  the  different  parts  of  the  system,  especially  to  those  which 
consume  this  gas  in  large  quantities,  that  is,  the  nerve  glob- 
ules, the  nerves,  and  the  muscles.  These  elements  give 
back,  in  exchange  for  the  oxygen  which  they  receive,  a  nearly 
equal  quantity  (see  respiration)  of  carbonic  acid,  a  small  part 
of  which  remains  in  the  blood  globules,  the  larger  part  being 
dissolved  in  the  liquid,  or  liquor  of  the  blood. 

The  functions  of  the  blood  globules  are  thus  principally 
mechanical,  on  account  of  the  movements  to  which  they  are 
subjected,  and  of  their  connection  with  the  gaseous  inter- 
change. We  may  also  say  that  the  principal  object  of  these 
functions  is  to  excite  or  support  the  nervous  system^  as  the 
nerves  can  exist  only  where  the  blood  globules  are  properly 
constituted,  and  contain  the  necessary  quantity  of  oxygen 
gas.  Thus  no  animal  can  lose,  unharmed,  more  than  one-fifth 
of  its  blood,  or  of  the  mass  of  its  cruor.  If  it  does,  it  suc- 
cumbs, with  symptoms  which  resemble  those  attending  a 
nervous  fever,  such  as  prostration,  loss  of  sensibility,  buzzing 
in  the  ears,  deafness,  convulsive  movements,  dyspnoea,  and 
death.  The  transfusion  of  fresh  blood,  defibrinated  (in  one 
word,  the  transfusion  of  globules),  will  remove  these  symp- 
toms, and  bring  back  life,  if  done  in  time ;  the  transfusion  of 
the  liquor  alone  will  not  suffice. 

The  transfusion  of  blood  consists,  essentially,  in  bringing  a 
new  supply  of  blood  globules.  This  operation  responds 
neither  to  the  exaggerated  hopes  of  the  restoration  of  youth, 
of  the  cure  of  madness,  etc.,  nor  to  the  unreasonable  fears 


122  THE  BLOOD  AND  ITS  CIRCULATION. 

which  it  excited  at  its  first  discovery  in  the  seventeenth 
century,  whence  the  practice  of  it  was  forbidden  by  the  Par- 
liament of  1668.  (Lower,  Denis.)  To-day,  we  count  by 
hundreds  cases  of  hemorrhage,  where  the  invalid  has  been 
recalled  to  life  by  the  transfusion  of  blood,  especially  in  the 
case  of  metrorrhagia.  In  order  to  produce  the  desired  effect, 
the  blood  globules  must  be  taken  from  an  animal  of  the  same 
kind.  Any  others  would  be  no  more  capable  of  restoring 
life  than  the  sperraatozoids  of  one  would  be  to  propagate  the 
ovula  of  the  other.  A  very  small  quantity  of  blood  is  suffi- 
cient to  produce  this  vital  change,  and  to  enable  the  patient 
to  regain  the  usual  quantity,  by  the  process  of  nutrition. 
Transfusion  has  also  been  applied  in  cases  of  poisoning,  and 
is  a  very  proper  agent  in  the  case,  for  instance,  of  poisoning 
by  oxide  of  carbon,  which  causes  paralysis  of  the  red  glob- 
ules; it  has  been  found  successful  (Rouget),  the  useless 
globules  being  replaced  by  new  ones  and  so  capable  of  their 
nutritive  and  respiratory  functions.  In  other  kinds  of  poison- 
ing and  in  the  uremia,  this  method  does  not  succeed  as  well. 

The  red  globules  are  thus  what  may  be  called  the  organ 
of  the  blood.  When  they  inci-ease  disproportionately,  a 
kind  of  plethora  ensues,  circulation  is  impeded,  and  conges- 
tion is  likely  to  follow.  Something  analogous  to  this  takes 
place  in  the  cholera,  but  by  an  entirely  different  method ; 
there  the  immense  waste  of  liquids  by  the  intestines  renders 
the  blood  extremely  thick ;  the  globules  uniting,  make  the 
blood  gluey.  In  all  chronic,  and  in  most  acute  diseases,  where 
a  strict  regimen  has  been  long  observed,  a  sensible  diminution 
takes  place  in  the  organ  of  the  blood  (see  p.  112),  corre- 
sponding with  the  length  of  the  malady.  It  attains  its  height 
in  anaemia  and  in  chlorosis,  and  cases  of  chlorosis  have  been 
known  in  which  the  cruor  formed  only  a  quarter  of  the  mass 
of  the  blood  ;  what  is  called  hydraemia  (a  corresponding  in- 
crease in  the  watery  part  of  the  blood  being  understood) 
then  takes  place. 

In  their  own  life,  the  blood  globules  exhibit  different 
phases  of  existence ;  they  undergo  changes ;  there  are  young 
globules,  and  old  globules.  The  former  are,  in  the  adult, 
produced  by  the  transformation  of  the  colorless  (the  white) 
globules  of  the  lymph. 

The  transformation  of  white  globules  into  red,  which  sonie 
histologists  consider  doubtful  is,  nevertheless,  shown  us  by 
many  proofs.  The  first  which  we  shall  mention  is  the  direct 
one  furnished   by  Recklinghausen,  and,  more  recently,  by 


THE  BLOOD.  123 

Kolliker,  who  have  seen  the  transformation  of  white  globules 
into  red  produced  even  outside  the  organism,  in  blood  kept 
at  the  temperature  of  the  living  body,  in  contact  with  a 
moist  atmosphere.  On  the  other  hand  the  study  of  the 
blood  in  the  animal  series  shows  all  the  transitions  between 
the  two  kinds  of  globules.  Rouget  has  shown  what  they  are 
in  the  case  of  the  invertebrate  animals,  the  sipunculi.  In  the 
inferior  vertebrate  animals,  particularly  the  tadpole  (Kolli- 
ker, Rouget),  we  observe  the  transformation  of  the  lymphatic 
corpuscles  into  colored  globules,  provided  with  a  nucleus, 
the  coloring  matter  being  first  deposited  under  the  form  of 
granulations,  and  then  spreading  uniformly,  throughout  the 
globules.  Rouget  has  observed  the  same  transformation  in 
the  embryo  of  rabbits ;  here  the  nucleus  diminishes,  and  at 
length  disappears,  while  the  coloring  matter  is  deposited 
first  in  patches,  and  afterwards  generally  diffused.  Finally, 
there  have  been  found  in  the  thoracic  duct,  and  even  in  the 
pulmonary  veins  (Kolliker)  young  red  globules  in  an  inter- 
mediate stage  between  the  white  globules  and  the  perfect 
red.  As  to  the  indirect  proofs  of  this  transformation,  it  will  be 
sufficient  to  remark  that  the  lymphatic  glands  and  the  spleen 
are  continually  pouring  white  globules  into  the  current  of 
the  blood.  Now,  as  we  do  not  find  that  their  number  in- 
creases in  the  blood,  and  know  of  no  proof  of  their  being 
destroyed,  we  are  forced  to  conclude  that  they  disappear  by 
being  changed  into  red  globules.  Finally,  these  red  glob- 
ules must  have  had  an  origin,  and  been  derived  from  a  pre- 
existing cell,  for  they  exhibit  globular  forms  which  are  already 
old,  the  loss  of  the  nucleus  and  the  presence  of  coloring 
matter  being  taken  into  account ;  if  we  accept  the  theory  of 
the  ge7iesis  for  the  production  of  the  white  globules,  which 
are  elements  in  an  early  stage,  we  cannot  do  the  same  in 
the  case  of  the  red,  which  are  old  forms  of  elements :  the 
early  stage  of  the  red  globules  can  be  represented  only  by 
the  white. 

In  their  mature  condition  the  red  globules  themselves  ex- 
haust  a  part  of  the  oxygen  with  which  they  are  charged, 
the  presence  of  this  oxygen  being  necessary  to  their  vitality 
and  to  their  form.  In  miaking  experiments,  whenever  it  is 
desired  to  filter  blood,  care  must  be  taken  to  introduce  into 
the  liquid  a  current  of  oxygen,  which  prevents  the  solution 
of  the  globules  in  the  liquor.  When  destroyed  in  the  sys- 
tem, the  globules  leave  what  are  evidently  the  products  of 
their  decomposition.    It  is  true  that  there  are  hardly  any 


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THE  BLOOD.  125 

what  we  know  of  the  physiology  of  the  liver :  the  latter,  on 
the  contrary,  agrees  perfectly  with  the  biliary  functions  of 
this  organ,  the  coloring  matter  of  the  bile  being  identical 
with  hematoidine,  one  of  the  derivatives  of  the  blood.  It  is 
useless  to  object  that  we  find  colored  bile  in  animals  whose 
blood  is  colorless  (the  invertebrate) ;  for  Rouget  has  found 
colored  globules  in  many  of  these  animals,  and  in  others 
liemoglobuline,  or  a  substance  analogous  to  it,  is  found  in  a 
diffuse  state,  dissolved  in  bloody  serum.  This  has  been 
proved  by  Fumouze,  by  the  aid  of  spectral  analysis,  even  in 
the  case  of  animals  whose  blood  appears  quite  colorless,  ^nd 
we  may  thence  conclude  that  the  liver  is  one  of  the  places  in 
which  the  old  red  globules  are  destroyed. 

Liquor.  —  The  liquid  part  of  the  blood  {liquor  or  plasma 
of  the  blood)  may  be  considered  as  a  solutioi^  of  albumen, 
containing  besides  several  salts,  fats,  extractive  matters,  and 
gases. 

The  liquor  is  a  fluid  comparatively  loaded  with  albumen, 
containing  nearly  one-tenth,  a  proportion  rarely  met  with  in 
the  other  fluids  of  the  system.  A  small  part  of  this  albu- 
men (2  grammes  to  1  litre  of  blood)  coagulates  spontane- 
ously: this  is  called ^^rme.  The  rest  (70  to  75  grammes  to 
a  litre  of  blood)  is  albumen,  properly  so  called,  which  coag- 
ulates only  by  the  action  of  heat  or  of  chemical  reagents. 

The  fibrine  is  the  cause  of  the  coagulation  of  the  blood, 
that  is  to  say,  of  the  phenomena  by  which,  on  leaving  the 
vessels,  the  blood  is  solidified  into  a  jelly-like  mass.  It  is  the 
fibrine  alone  which  is  coagulated  in  this  case,  and  forms  a  kind 
of  net  in  which  the  other  elements  of  the  blood,  and  espe- 
cially the  globules,  are  imprisoned.  We  do  not  mean  by 
this  that  the  fibrine  becomes  a  fibre,  as  its  name  would  ap- 
pear to  indicate ;  it  forms,  rather,  a  sort  of  spongy  mass, 
containing  in  its  meshes  all  the  other  parts  of  the  blood. 
As  coagulation  proceeds  the  liquid  part  takes  the  form  of 
serum^  a  limpid  or  slightly  opaline  liquid,  which  contains 
albumen  and  the  various  salts  of  the  liquor;  the  coagulated 
mass  which  floats  forms  the  clot.  The  clot  must  not  be  con- 
founded with  the  cruor ;  it  is  the  fibrine  containing  the 
cruor :  neither  is  the  seru7n  synonymous  with  the  liquor,  it 
being  the  liquor  without  the  fibrine. 

It  is  not  ascertained  what  circumstances  are  most  favor- 
able to  the  coagulation  of  the  blood.  It  is  hindered  by  cold, 
and  accelerated  by  contact  with  the  air.  Beating,  which  is 
employed  to  defibrinate  th^  blood,  acts  only  by  rendering 


126 


THE  BLOOD  AND  ITS   CIRCULATION. 


the  contact  between  the  au*  and  the  fibrine  closer  and  more 
general.  By  this  means  the  fibrine  coagulates  rapidly,  and 
hangs  in  shreds  from  the  instrument  employed.  The  globules 
appear  to  have  some  share  in  this  phenomenon,  and  seem  to 
aid  in  solidifying  the  fibrine.  We  know  that  coagulation 
is  retarded  by  the  mixture  with  the  blood  of  such  substances 
as  sugar,  salt,  or  any  alkali.  In  this  case  a  certain  number 
of  the  globules  do  not  become  enclosed  in  the  fibrine,  but 
color  the  serum  red,  while  the  clot  is  paler,  or  even  quite 
white,  in  its  upper  coats  (couenne) :  these  fibrous  buffy  coats 
are  also  found  in  some  pathological  conditions,  in  diseases  of 
the  lungs,  for  instance,  and  here  we  find  the  fibrous  sponge 
enclosing  globules  covered  with  a  layer  of  pure  fibrine,  which 
has  a  whitish  tint,  or  is  coated,  thus  containing  the  white 
globules  (which,  by  their  lightness,  have  a  tendency  to  rise 
to  the  surface)  (Fig.  36).  This  phe- 
nomenon   may    have    two    different 

^ fiL— f*     causes,  independently   of  an    excess 

ll^^^^^^^  of  fibrine:  either  the  blood  globules 
(the  red)  have  become  specifically 
heavier,  or  coagulation  is  slower.  In 
the  former  case  they  are  not  at  the 
same  level  in  the  liquid  as  the  fibrine 
which  floats  and  coagulates  apart:  in 
the  latter  they  have  time  to  sink, 
while  the  fibrine  coagulates  slowly. 
In  horses  coagulated  blood  shows 
always  a  buffy  coat. 

The  fibrine  was  formerly  looked 
upon  as  a  most  important  part  of  the 
system :  it  was  considered,  on  the  one 
hand,  to  be  the  nutritive  substance, 
par  excellence,  perfected  albumen;  on  the  other,  to  be  a 
part  of  the  organization,  on  account  of  the  apparently  fibrous 
structure  which  it  exhibits  when  coagulated.  At  present  it 
is  admitted  that  this  is  a  mistake :  fibrine  is  rarely  found  in 
the  most  nutritive  substances,  and  the  quantity  in  the  blood 
does  not  increase  with  the  increased  vigor  of  the  subject ;  on 
the  contrary,  it  is  found  to  accumulate  after  fisting,  after  a 
fatiguing  walk,  in  diseases  where  there  is  great  emaciation, 
in  cases  of  want  of  nutrition,  in  chlorosis,  etc.     It  is  more 

*  a,  Level  of  the  liquor  sanguinis,  c,  Buffy  coat,  in  the  fonn  of  a  cup. 
tj  Granular  layer,  with  granular  collection  of  white  globules,  r.  Clot,  with  red 
globules.    (Cl*uor  and  red  clot.)    (Virchew,  "  Pathologic  Cellulaire.") 


Fig.  36— Coagulated  blood 
with  a  buffy  coat.* 


THE  BLOOD.  127 

abundant  in  adults  than  in  children.  When  an  animal  is 
bled,  and  thus  deprived  of  a  large  quantity  of  fibrine,  it  is 
easily  ascertained  that  the  fibrine  is  reproduced  shortly  after- 
wards. Thus  it  does  not  come  from  outside :  it  is  formed  in 
the  organism,  and  examination  of  the  circumstances  under 
which  it  increases  proves  that  it  constitutes  an  organic  waste 
which  gives  rise  by  its  decomposition  to  the  urea  and  to  uric 
acid  :  these  elements,  in  fact,  appear  in  the  urine  after  inflam- 
mations in  which  there  has  been  an  excess  of  fibrine  in  the 
blood. 

The  experiments  of  Brown-Sequard  show  that  in  the  phys- 
iological condition  fibrine  is  produced,  above  all,  in  the 
muscles,  and  that  the  blood  which  comes  from  a  muscle  is 
richer  in  fibrine  the  more  the  muscle  has  been  exercised,  as, 
for  instance,  when  under  the  influence  of  galvanism.  Fibrine 
is,  then,  an  excrementitious  form  of  the  products  of  nutrition 
of  the  tissues,  being  found  in  greater  abundance  when  the 
tissue  has  receiyed  more  nutrition.  It  is  difiicult  to  decide 
where  the  fibrine  disappears  or  is  destroyed.  It  has  been 
supposed  that  there  is  no  fibrine  in  the  blood  which  comes 
from  the  liver.  This  is,  however,  an  error.  The  blood  or 
the  liver  is  as  rich  in  fibrine  as  that  of  the  spleen  or  the 
muscles,  and  it  only  appears  to  be  without  it  when,  in  dissec- 
tion, the  bile  is  allowed  to  mix  with  the  blood  drawn  from 
this  organ  (Vulpian).  Too  severe  labor,  or  organic  combus- 
tion, always  produces  an  excess  of  fibrine  in  the  blood ;  in 
all  inflammation  there  is  hyperinosis ;  this  hyperinosis  is 
entirely  secondary,  and  not  at  all  the  cause  of  the  state  of 
fever  or  inflammation.  In  efiusions  no  fibrine  is  found,  unless 
the  neighboring  tissues  are  in  a  state  of  inflammation  capable 
of  giving  rise  to  an  excess  of  this  organic  waste :  thus,  the 
liquid  of  hydrothorax  contains  no  fibrine ;  that  of  pleurisy, 
on  the  contrary,  a  great  deal,  etc. 

The  liquid  which  remains  after  the  coagulation  of  the 
fibrine  is  called  the  serum.  It  contains,  as  we  have  already 
said,  a  large  proportion  of  albumen  (between  70  and  75 
grammes  to  1000  parts)  which  does  not  coagulate  sponta- 
neously. The  serum  finds  its  way  easily  out  of  the  vessels 
either  by  osmosis,  or  more  frequently  by  simple  transudation, 
because  in  cases  of  stoppage  of  the  blood  by  a  ligature  or  by 
compression  it  has  been  observed  that  the  albumen  abun- 
dantly transudes.  It  is  generally  supposed  that  the  object 
of  the  normal  transudation  of  the  albumen  is  the  nutrition 
of  the  tissues ;  this,  however,  is  by  no  means  certain ;  and. 


128  TEE  BLOOD  AND  ITS  CIRCULATION. 

indeed,  we  find,  in  addition  to  the  albumen,  a  series  of 
albuminoid  substances  called  peptones^  not  coagulable  by 
heat,  and  appearing  particularly  well  adapted  for  transforma- 
tion easily  and  readily  into  the  form  of  tissue.  It  is  more 
likely  that  the  principal  use  of  ordinary  albumen  is  to  pre- 
vent the  adhesion  of  the  blood  to  the  coats  of  the  vessels. 

The  serum  contains  various /a^^y  matters.  In  some  cases 
it  is  difficult  to  account  for  the  presence  of  these  fats.  Thus, 
in  the  case  of  persons  who  are  habitual  inebriates,  drops  of 
fat  are  sometimes  found  floating  in  the  blood;  after  an  abun- 
dant meal,  also,  an  accumulation  of  fatty  globules  is  found  in 
the  blood,  which,  however,  soon  disappear.  A  fatty  sub- 
stance, also,  which  is  not  capable  of  saponification,  is  gen- 
erally found  in  the  serum  (cholesterine)  ;  this  is  admitted  to 
be  an  excrementitious  product  (to  be  rejected  by  the  liver). 
In  addition  to  these  fats  are  found  the  fatty  elements  (mar- 
garine, oleine ;  margarates  and  oleates  of  soda)  and  fat  acids 
peculiar  to  each  animal,  and  which  may  be  removed  by  means 
of  sulphuric  acid.  These  volatile  fat  acids,  when  thus  re- 
moved, emit  a  peculiar  odor,  by  means  of  which  the  blood 
of  man  can  be  distinguished  from  that  of  other  animals,  and 
it  has  even  been  asserted,  the  blood  of  a  man  from  that  of  a 
woman.  The  sum  total  of  fatty  matters  contained  on  an 
average  in  the  blood  is  from  2  or  3  grammes  in  a  litre. 

There  are,  besides,,  found  in  the  liquor  some  compositions 
which  it  is  difficult  to  classify,  known  by  the  name  of  extrac- 
tive matters.  Among  these  complex  substances  we  will  men- 
tion the  lactic  acid  and  the  lactates^  which  are  formed,  no 
doubt,  principally  during  the  process  of  digestion ;  also,  the 
pneumic  acid,  whose  existence  is  still  doubtful,  but  which  is 
probably  due  to  a  reaction  in  the  lung,  which  releases  the 
carbonic  acid  from  the  venous  blood ;  also,  the  urea  and  uric 
acid,  excrementitious  products  destined  to  be  thrown  off, 
whose  retention  in  the  blood  is  highly  dangerous ;  also,  the 
creatine  and  creatinine. 

We  must  also  mention  here  the  coloring  matters  which, 
no  doubt,  originate  in  the  globules,  reappearing  in  some 
secretions,  especially  in  the  bile ;  and,  finally,  those  composi- 
tions, belonging  to  the  class  of  sugars,  which  arise  partly 
from  the  ingested  substances,  and  partly  also,  perhaps,  from 
the  transformations  which  take  place  in  the  different  tissues, 
glands,  and  particularly  in  the  liver ;  their  function  is,  per- 
haps, more  essentially  glycogenic  (see  "  digestion ;  functions 
of  the  liver"). 


THE  BLOOD.  129 

The  salts  contained  in  the  serum  (and  consequently  in 
the  liquor)  are  not  identical  with  those  which  we  have  de- 
scribed as  found  in  the  globules.  The  salts  contained  in  the 
blood  form  8  or  10  in  1000  parts,  the  principal  portion  being 
of  an  alkaline  character.  Soda,  especially  in  the  form  of  car- 
bonate, is  the  basis  of  most  of  the  salts  in  the  liquor.  The 
serum  is  extremely  alkaline,  and  the  necessity  of  this  reaction 
is  plain,  if  we  remember  all  the  reductions  to  be  made  in  this 
liquid.  There  are,  besides,  few  metals  whose  presence  has 
not  been  suspected  in  the  blood  {liquor  and  cruor)  ;  iron  and 
manganese  have  been  found  in  it,  and  occasionally  copper, 
which  we  might,  perhaps,  consider  a  normal  constituent.  It 
is  also  asserted  that  arsenic  has  been  discovered ;  lead  rarely : 
these  are,  however,  simply  chemical  curiosities.  (These  last- 
named  substances  exist  in  such  minute  quantities  that  we 
might  leave  them  out  of  consideration.     Am.  ed.) 

Gases  of  the  Blood.  —  Blood  contains  not  only  solids 
and  liquids,  but  gases  also.  Considered  in  regard  to  respira- 
tion the  blood  is  really  a  solution  of  gas.  1.  We  have 
already  seen  that  the  red  globule  is  the  medium  of  a  certain 
quantity  of  oxygen.  A  smaller  proportion  of  the  same  gas 
is  dissolved  in  the  liquor.  2.  The  carbonic  acid  is  contained 
wholly  in  the  serum,  partly  in  a  state  of  solution,  partly 
combined  with  the  alkaline  carbonates,  which  thus  pass  into 
the  state  of  bi-carbonates  (Emile  Fernet).^  We  shall  study 
the  gases  of  the  blood  more  fully  when  we  come  to  the  sub- 
ject of  respiration,  and  we  shall  thus  discover  that  the  blood 
is  the  essential  vehicle  of  those  gases,  which  supply  the  com- 
bustion of  the  tissues  or  may  be  the  result  of  combustion. 

The  question  of  the  albuminoid  substances  of  the  blood  is  one 
of  those  which  have  been  the  most  studied,  and  yet  is  far  from 
being  completely  elucidated.  It  is  now  proved  that  the  fibrine  is 
not  produced  in  the  globules,  as  was  formerly  believed,  and  that  it 
does  not  represent  a  substance  dissolved  in  the  blood,  either  by  the 
action  of  chloride  of  sodium  or  of  ammonia  (Richardson),  though 
the  liquefying  action  of  these  substances  is  undeniable.  Robin 
and  Verdeil  had  already  demonstrated  (1851)  that  tibrine  does  not 
pre-exist  in  the  blood  as  a  concrete  substance,  but  naturally  is  in  a 
liquid  state,  and  generally  only  ceases  to  be  so  when  taken  from 
the  system.  Now,  however,  we  go  further,  and  recent  researches, 
which  are  still  incomplete,  lead  us  to  look  upon  it  as  the  result  of 

*  Emile  Fernet,  "  Du  Role  des  Principaux  Elements  du  Sang 
dans  1' Absorption  ou  le  Degagement  des  Gaz  de  la  Respiration." 
Paris,  1858,  in  4to. 


130  TUE  BLOOD  AND  ITS   CIRCULATION. 

a  decomposition,  until  its  relation  to  those  other  albuminoid  sub- 
stances found  with  it  in  the  liquor  of  the  blood  is  more  fully  estab- 
lished. 

We  shall  not  speak  of  the  theory  of  Bechamp  and  Est-or,  who 
maintain  that  the  fibrine  is  formed  by  the  union  of  those  organic 
living  molecules  which  they  have  termed  rnlcrozymas.  These  re- 
searches have  not  yet  been  established  by  observed  facts  and  experi- 
ments, which  form  the  ordinary  domain  of  science.  Denis  (of 
Commercy),  in  France,  and  Schmidt,  in  Germany,  have  found 
similar  results  in  a  series  of  researches  which  were  extremely 
fruitful  in  pathological  applications,  and  are  so  important  that  we 
cannot  resist  giving  a  short  resume  oi  them,  in  order  to  complete 
the  study  of  the  serum. 

According  to  Schmidt  and  Denis  (of  Commercy),  the  albumi- 
nous part  of  the  blood  is  composed  of  two  substances,  of  which  one, 
serine  (52  to  1000  of  blood),  coagulates  only  by  the  action  of  heat 
or  of  acids;  the  other,  plasmine  (25  to  1000  of  blood),  coagulates 
under  the  influence  of  chloride  of  sodium,  and  may  be  redissolved 
in  from  10  to  20  parts  of  its  weight  of  water.  A  part  of  the  solu- 
tion, however,  as  of  the  original  plasmine,  may  separate  sponta- 
neously and  coagulate;  this  is  concrete  f  brine  (3  or  4  to  1000  parts  of 
blood) :  the  rest  remains  dissolved,  but  coagulates  under  the  influ- 
ence of  sulphate  of  magnesia;  this  is  dissolved  Jibrine  (22  to  1000 
parts  of  blood).  The  coagulation  of  the  blood  is  thus  the  result  of 
the  separation  of  the  plasmine  into  dissolved  and  concrete  fibrine. 
The  variations  in  the  quantity  of  fibrine  in  coagulated  blood  are 
entirely  owing  to  a  decomposition  which  divides  the  plasmine  more 
or  less  unequally  into  its  two  products.  When  we  find  an  excess 
of  concrete  Jibrine  (8  grammes,  for  instance),  there  is  a  diminution 
of  the  dissolved  fibrine  (17  only  in  the  example  chosen),  and  vice 
versa. 

W«  can  understand,  in  this  way,  all  that  was  still  obscure  in 
physiology,  as  the  pathology  of  the  coagulation  of  the  blood. 
Thus  the  blood  which  comes  from  the  liver  apparently  contains  no 
fibrine;  but  if  its  plasmine  be  precipitated  by  chloride  of  sodium, 
and  the  coagulum  dissolved  in  from  10  to  20  parts  of  its  weight  of 
water,  the  normal  quantity  of  concrete  fibrine  (2  to  4  gr.)  will  be 
precipitated,  either  spontaneously  or  by  beating.  The  plasmine  of 
the  blood  from  the  liver  thus  contains  the  two  kinds  of  fibrine, 
but  a  cause,  which  it  is  still  difficult  to  decide  (see  p.  127,  above), 
has  prevented  their  separation,  and  concealed  the  existence  of  the 
concrete  fibrine,  as  it  was  formerly  known.  On  the  other  hand, 
we  recognize,  as  a  general  rule,  the  increased  size  of  the  clot  and 
of  fibrine  in  inflammations.  There  are  some  inflammations,  how- 
ever, in  which  we  think  we  discover  some  diminution  in  the  coag- 
ulable  element,  hypinosis ;  but  here  also  concrete  fibrine  prevails 
over  dissolved  fibrine  in  the  composition  of  the  plasmine,  and 
appears  immediately,  if  a  separation  of  the  latter  and  formation  of 
the  clot  be  artificially  produced  (precipitation  by  chloride  of  sodium, 
solution  in  10  times  its  weight  of  water,  exposure  to  the  air,  beating, 


CIRCULATION  OF  THE  BLOOD.  131 

etc.).  We  may  thus  conclude,  with  Germain  S6e  ("  Pathologie 
Experimentale:  "  Anemies),  that,  as  a  general  rule  in  diseases,  espe- 
cially where  there  is  anaemia,  there  is  really  neither  an  excess  or  a  want 
of  fibrine,  but  the  plasmine  is  more  or  less  perfect,  that  is,  more  or 
less  easily  divided  into  two  elements,  thus  partaking  of  its  nature 
in  different  degrees.  Finally,  according  to  Vulpian,  all  the  albu- 
minous parts  of  the  blood  form  probably  a  composition,  two  parts  of 
which,  serine  and  plasmine  (with  its  two  elements)  are  the  result 
of  a  division,  as  alcohol  and  carbonic  acid  are  produced  in  the 
analysis  of  sugar.  This  explanation  throws  fresh  light  on  the 
pathogeny  of  albuminuria,  especially  of  that  sort  caused  by  changes 
in  the  albumen  of  the  blood,  and  of  albuminuria  occurring  after 
the  artificial  ingestion  or  injection  of  albumen,  even  of  albumen 
taken  previously  from  the  blood  of  the  animal.  (Experiment  of 
CI.  Bernard,  of  Stokvis,  of  Calmettes.) 

Circulation  of  the  Blood. 

The  circulation  consists  of  the  continued  movement  of  the 
blood  in  a  circular  reservoir  formed  of  ramified  tubes  (circu- 
latory apparatus).  This 
apparatus,  looked  at  as 
a  whole,  is  simply  a  series 
of  tubes,  with  different 
functions  and  properties 
(Fig.  37).  These  are: 
1.,  The  heart,  a  muscu- 
lar reservoir,  divided 
into  four  cavities  (in 
man,  but  more  simple 
in  the  lower  animals). 
At  first  it  also  forms  a 
cylindrical  tube,  which 
during  the  life  of  the 
embryo  becomes  twisted, 
and  is  divided  so  as  to 
form  the  auricles  and 
the  ventricles.  2.  The 
arteries,  a  system  of 
ramified    tubes,   in    the 

.    /,  '  1     v,i    '<•      fi  Fig.  37.— Plan  of  the  circulating  system* 

cially  remarkable  tor  the 

thickness  and  strength  of  their  coats  (Fig.  37,  a).     3.   The 

veins,  another  system  ramified  like  that  of  the  arteries,  but 

*  C R,  Heart,  ventricle  (o,  auricle;   s,  s,  valves),     a,  Arteries.     CP,  Capil 
laries.    /»,  Veins.     The  arrows  show  the  direction  in  which  the  litiuid  flows. 


132  THE  BLOOD  AND  ITS  CIRCULATION, 

distinguished  from  the  latter  by  the  thinness  and  flaccidity 
of  their  coats  (Fig.  37,ji?).  4.  Between  these  two  systems 
is  the  capillary  system  (beginning  in  the  arteries  and  ending 
in  the  veins),  a  collection  of  very  fine  vessels,  arranged  like 
the  string  in  a  net  (Fig.  37,  C  P),  the  smallest  having  gen- 
erally the  same  diameter  as  the  blood  globules)  ;  their  calibre 
is  even  less  sometimes,  but  the  globules  being  elastic  can 
become  so  long  and  thin  that  they  can  traverse  tubes  much 
smaller  than  themselves. 

The  whole  of  the  circulatory  system  may  thus  be  divided 
into  a  central  organ,  the  heart,  and  a  number  of  peripheral 
organs,  the  vessels  (arteries,  capillaries,  veins). 

The  blood  circulates  in  a  system  of  vessels,  because  at  the 
beginning  of  this  system  (origin  of  the  aorta)  is  found  one 
of  the  cavities  of  the  heart,  which  possesses  the  property  of 
producing  a  strong  pressure  (the  ventricle),  while  at  the 
other  extremity  (vena  cava)  is  found  another  cavity  of  the 
heart  (the  auricle),  whose  property  it  is  to  diminish  the  pres- 
sure, or  at  least  to  allow  a  free  passage  to  the  blood  which  it 
receives,  in  order  to  transmit  this  fluid  to  the  ventricle ;  by 
this  double  antagonism  between  the  two  cavities  of  the  heart 
the  circulation  is  produced. 

In  short,  the  circulation  of  the  blood  is  caused  by  the  in- 
equality of  pressure  in  the  different  parts  of  the  vascular 
circuit,  and  the  use  of  the  heart,  taken  as  a  whole  (auricles 
and  ventricles),  is  to  keep  up  this  inequality  of  pressure, 
which  makes  the  blood  pass  from  the  arteries  where  the 
pressure  is  strong  into  the  veins  where  it  becomes  gradually 
weaker. 

The  ideas  entertained  by  the  ancients  as  to  the  circulation 
of  the  blood  were  false  and  incomplete.  Galen  supposed  the 
blood  to  be  formed  in  the  liver,  and  that,  on  leaving  this 
organ,  it  spread  through  the  lower  part  of  the  body  by 
means  of  the  inferior  vena  cava,  and  through  the  upper  part- 
by  means  of  the  superior  vena  cava:  that,  as  a  portion  of 
this  latter  blood  reached  the  heart,  and  filtered  through  the 
interventricular  partition,  it  acquired  new  properties,  by 
means  of  which  it  circulated  through  the  arteries  under  the 
name  of  vital  spirits.  G^len  had  thus  no  suspicion  of  the  ex- 
istence of  the  pulmonary  circulation  (see  farther  on,  p.  142). 

The  idea  of  jmlmonary  circulation  was  first  suggested  by 
Michel  Servet,  in  1553.  Fabrice,  of  Acquapendente,  first 
demonstrated  the  arrangement  of  the  venous  valves,  which 
contradicted  the  theory  of  circulation,  as  conceived  by  Galen. 


CIRCULATION.  — THE  HEART.  133 

Harvey  finally  (1615-1628)   established  the  theory  of  the 
circulation  of  the  blood  as  we  hold  it  at  this  day. 


I.    Of  the  Central  Organ  of  the  Circulation  ;  of  thh 

Heart. 

In  order  to  comprehend  the  functions  of  the  heart  we 
must  not  think  of  it  as  we  find  it  in  the  dead  body,  for  there 
is  no  trace  there  of  the  muscular  elasticity^  which  is  one  of 
the  most  important  properties  of  a  muscle,  just  as  important 
as  the  contractility.,  and  having  a  special  purpose  in  that  cav- 
ity of  the  heart  called  the  auricle. 

Auricle.  —  The  chief  function  of  the  auricle,  on  account  of 
its  power  of  dilatation,  is  to  facilitate  the  flow  of  the  venous 
blood ;  it  may  be  said  to  have  the  same  effect  as  blood-letting 
at  the  extremity  of  the  venous  system^  by  which  the  pressure 
of  the  fluid  is  consequently  diminished.  During  four-fifths 
of  the  time  occupied  by  a  cardiac  revolution  the  auricle  is  in 
a  state  of  repose,  and  fills  with  blood,  or  rather,  allows  itself 
to  be  filled,  for  it  exercises  little  or  no  active  aspiration  on 
the  venous  blood  (see  Respiration).  It  resembles,  at  this 
moment,  a  soap-bubble,  distended  by  air  blown  into  it :  thus 
it  becomes  the  receptacle  of  the  blood,  the  ante-chamber  of 
the  ventricle,  a  receptacle  wherein  a  large  quantity  of  blood 
accumulates;  and  the  auricular  capacity  being  greater  than 
that  of  the  ventricle,  which  it  can  immediately  fill  without 
itself  becoming  completely  emptied. 

When  the  auricle  is  full  of  blood  it  contracts  suddenly, 
and  drives  the  blood  towards  the  ventricle,  as  it  were,  in  the 
twinkling  of  an  eye.  Its  contraction  lasts  from  one-fourth 
to  one-fifth  of  the  total  cycle.  Supposing  that  the  heart  con- 
tracts sixty  times  in  a  minute,  the  contraction  of  the  auricle 
would  last  only  one-fourth  or  one-fifth  of  a  second,  the  rest 
of  the  time  being  in  a  state  of  repose.  By  computing  its 
times  of  activity  and  repose,  we  might  say  that  the  auricle 
is  relaxed  during  eighteen  hours  out  of  the  twenty-four. 

The  contraction  of  this  cavity  tends  to  throw  its  contents 
towards  the  ventricle,  or  to  return  them  to  the  veins.  There 
are  no  valves  in  the  direction  of  the  veins  (Eustachian  valve 
being  excepted),  or  they  are  placed  at  a  distance,  and  are 
consequently  incapable  of  preventing  this  reflux;  but  the 
veins  are  full  of  blood,  under  feeble  pressure,  it  is  true,  but, 
nevertheless,  some  resistance  is  thus  ofiered  to  the  return  of 
the  auricular  contents.     The  condition  of  the  ventricle  is  at 


134  THE  BLOOD  AND  ITS   CIRCULATION. 

this  time  entirely  different ;  it  is  empty,  completely  relaxed, 
and,  consequently,  offers  no  resistance  whatever:  the  part 
which  it  now  plays  in  regard  to  the  auricle  is  the  same  as 
that  previously  sustained  by  the  auricle  in  regard  to  the 
veins ;  and  the  elasticity  of  the  muscle^  when  i?i  a  state  of 
repose,  allows  the  ventricle  to  be  distended  (see  physiology 
of  the  muscle,  p.  81)  with  as  little  resistance  as  would  be 
offered  by  a  soap-bubble.  Thus  the  blood  of  the  contracted 
auricle,  meeting  with  a  slight  resistance  from  the  veins,  and 
none  at  all  from  the  ventricle,  is  precipitated  into  the  latter, 
and  fills  it.  If  the  muscular  tissue  of  the  ventricle  is  dis- 
eased, and  its  elasticity  diminished,  a  certain  reflux  will 
sometimes  take  place  into  the  veins,  which  is  one  of  the 
causes  of  the  pathological  venous  pulse :  this  venous  pulse 
always  exists  to  a  slight  degree,  but  is  usually  scarcely  per- 
ceptible. 

The  auricle  is  not,  however,  completely  emptied,  and  its 
opposite  sides  do  not  come  in  contact  with  each  other.  Its 
rapid  contraction  being  terminated,  resumes  the  position  of  a 
passive  organ,  and  allows  the  blood  which  tills  the  venous 
system  to  flow  freely  into  its  cavity. 

Ventricle.  —  The  ventricle  is  hardly  full  before  the  blood, 
by  its  contact  with  the  walls  of  this  cavity,  occasions  their 
contraction.  The  ventricular  systole  thus  immediately  suc- 
ceeds the  auricular  systole ;  but  the  former  lasts  a  long  time., 
because  the  ventricle  is  obliged  to  empty  its  contents  into 
a  cavity  which  is  already  full  of  blood,  and  which  offers 
some  resistance  to  the  entrance  of  more.  By  this  contrac- 
tion and  prolonged  effort  the  contents  of  the  ventricle  pass 
into  the  corresponding  artery  without  any  reflux  towards  the 
auricle. 

How  is  this  reflux  towards  the  auricle  prevented?  By 
means  of  a  special  apparatus  called  the  auriculo-ventricular 
valves,  which  really  form  a  sort  of  sleeve  or  bag  hanging 
from  the  edges  of  the  auricle  into  the  ventricle,  and  alter- 
nately approaching  and  withdrawing  from  the  walls  of  the 
latter.  The  name  "  valve  "  shows  that  the  r6le  of  this  organ  ^ 
was  not  at  first  understood.  It  is  now  shown  that  the  tri- 
cuspid or  mitral  valve  does  not  serve  as  a  plug,  but  is  only  a 
movable  continuation  of  the  auricle,  acted  upon  by  certain 

'  See  V.  L.  Kohl,  "  Etude  Critique  sur  la  Physiologie  de  I'Ap- 
pareil  Auriculo-ventriculaire.  These  de  Strasbourg,  18G9,  No. 
231. 


CIRCULA  riON.  —  THE  HEART. 


135 


muscular  powers.  In  fact,  a  large  number  of  papillary 
muscles^  having  as  many  as  100  tendons  in  the  right  heart, 
and  120  in  the  left,  are  inserted  in  the  edges  and  external 
surface  of  this  auriculo-ventricular  apparatus.  When  the 
ventricle  contracts,  these  papillary  muscles  also  come  into 
play.  It  was  formerly  supposed  that  these  muscles  and  the 
tendons  belonging  to  them  must  serve  to  prevent  the  sup- 
posed valve  from  being  too  much  stretched  in  consequence  of 
a  retrograde  effort  of  the  blood,  and  from  being  turned  wrong 
side  out  in  the  auricular  cavity.  But  their  function  is  entirely 
different,  for  if  the  finger  be  introduced  into  the  auriculo- 
ventricular  region  at  the  moment  of  the  systole  of  the  ven- 
tricle, we  find  that  the  kind  of  funnel  which  hangs  from  the 
auricle  to  the  ventricle  is  continued;    it  even  appears  to 


Fig.  38.  —  Showing  the  auriculo- 
ventricular  system  during  the 
repose  of  the  ventricle.* 


•Showing  the  auriculo-ventricu- 
apparatus  during  the  contraction 
of  the  ventricle,  t 


lengthen  itself  out,  and  the  finger,  as  it  were,  is  drawn  into 
the  interior  of  the  ventricle.  In  fact,  the  first  result  of  the 
contraction  of  the  papillary  muscles  is  the  lengthening  of 
the  auricular  cone,  the  edges  of  which  are  afterwards  brought 
near  each  other.  While  this  hollow  cone  descends  into  the 
ventricle,  the  sides  of  the  latter  contract,  and  approach  the 
cone  in  such  a  manner  that  the  auriculo-ventricular  apparatus 
acts  as  a  sort  of  hollow  piston,  which  penetrates  the  ventri- 
cle and  comes  into  close  contact  with  its  walls,  and  thus  the 


*  V,  Vein.  0,  Auricle.  V,  Coats  of  the  ventricle,  with  the  papillary 
muscles  and  their  tendons.  A,  Artery.  1,  Cavity  of  the  auriculo-ventricular 
apparatus.    2,  Infundibulum. 

t  1,  During  the  first  half  of  the  ventricular  systole.  2,  At  the  end  of  this 
Bvstole.  A  V,  Tiie  hollow  piston  formed  bv  the  auriculo-ventricular  apparatus. 
O  Auricle.    V,  Coats  of  the  ventricle.    A,  tulmonary  artery  and  (arterial)  aorta. 


136  THE  BLOOD  AND  ITS   CIRCULATION. 

ventricle  (Fig.  39)  empties  itself  completely,  the  contact 
becoming  perfect  between  its  sides  and  the  auricular  prolon- 
gation. 

The  result  of  this  mechanism,  which  is  so  simple,  and  yet 
80  generally  misunderstood,  is  that  no  reflux  of  blood  into 
the  auricle  can  take  place :  the  auricle,  even  by  means  of 
the  mechanism  which  we  have  described,  exercises  a  sort  of 
suction  upon  the  venous  blood,  its  cavity  being  continued  so 
far  into  the  ventricle.  We  see,  also,  that  when  the  ventricu- 
lar systole  is  complete,  the  lengthened  tube,  the  hollow  cone 
which  unites  the  ventricle  and  the  auricle,  is  full  of  blood, 
and  that  a  slight  and  rapid  contraction  of  the  auricle  is  suffi- 
cient to  drive  this  blood  into  the  ventricle  and  fill  it. 

Nearly  all  the  standard  works  admit,  without  discussion, 
the  theory  of  the  occlusion  of  the  auriculo-ventricular  ori- 
fices by  the  simple  mechanism  of  a  plug  or  valve,  just  as  in 
the  case  of  the  arterial  orifices  (see  farther  on),  but  without 
remarking  the  entire  difference  of  structure  which  distin- 
guishes the  auriculo-ventricular  valves  from  the  semilunar 
valves  of  the  aorta  and  of  the  pulmonary  artery.  This 
theory  has  become,  up  to  a  certain  point,  the  property  of 
Chauveau  and  Faivre,  on  account  of  the  interesting  experi- 
ments which  they  have  so  often  made  upon  horses,  killed 
instantaneously  by  section  of  the  bulb,  and  in  which  artifi- 
cial respiration  was  kept  up.  "  li\  under  these  circumstances, 
the  finger  is  introduced  into  one  of  the  auricles,  and  the 
auriculo-ventricular  orifice  explored,  the  tricuspid  valves 
will,  at  the  moment  that  the  ventricles  begin  to  contract,  be 
felt  to  straighten,  appose  their  edges,  and  stretch  in  such 
a  manner  as  to  become  convex,  and  form  concave  domes 
above  the  ventricular  cavity."  This  method  of  proof 
does  not  always  furnish  such  decided  results;  the  finger 
thus  introduced  has  given  to  many  other  observers  quite 
different  sensations.  Onimus  found  the  auriculo-ventricular 
orifices  eff*aced  by  the  contraction  of  the  muscular  fibres, 
which,  at  this  level,  really  form  a  spliincter  (this  is  the  case 
in  the  heart  of  birds,  but  not  of  the  mammalia).  The 
papillary  muscles,  being  now  contracted,  lower  the  valves, 
and  these,  pressing  themselves  against  the  sides  of  the 
ventricles,  have  the  effect  of  driving  the  blood,  engulfed 
between  them  and  the  corresponding  sides,  into  the  arterial 
orifices.  Such  is,  in  short,  the  working  of  the  auriculo-ven- 
tricular membranes.  This  is  the  only  theory  which  accounts 
for  the  existence  and  arrangement  of  the  papillary  muscles. 


CIRCULATION.  — THE  HEART,  137 

It  was  first  suggested  by  Parchappe  (1848) ;  was  chiefly 
developed  by  Burdach ;  afterwards  by  Purkinje  and  Nega 
(1852);  more  recently  by  Malherbe  (Nantes)  and  Fossion ; 
and  admitted  by  J.  Beclard  ("  Physiologic,"  6th  ed.,  1870). 
Now,  it  appears  incontestable  that  the  contraction  of  the 
papillary  muscles  transforms  the  auriculo-ventricular  cone, 
that  is,  the  infundibulum  left;  between  the  opposite  sides 
of  the  valves,  into  a  veritable  tendinous  cord,  more  or  less 
hollow,  between  the  interstices  of  which  the  blood  is  un- 
able to  make  a  passage  by  which  it  may  flow  back  into  the 
auricle.^ 

What  becomes  of  the  blood  thus  pressed  between  the 
sides  of  the  ventricle  and  the  hollow  piston  which  penetrates 
its  cavity  ?  Under  the  influence  of  the  contraction  of  the 
ventricle  and  of  the  working  of  the  auriculo-ventricular  sys- 
tem, which  acts  as  an  expulsive  apparatus^  the  cavity  of  tlie 
ventricle  has  a  tendency  to  completely  disappear,  even  to  its 
base,  by  means  of  the  fleshy  columns  (columnae  carnise) 
whose  contractions  bring  the  edges  of  this  base  in  contact 
with  that  of  the  auricular  plunging  cone.  The  blood,  being 
unable  to  return  into  the  auricle,  must  escape  by  the  arterial 
orifice  of  the  ventricle  (pulmonary  artery  or  aorta).  We 
must,  however,  observe  that  these  arteries  are  already,  by 
means  of  the  foregoing  contraction,  filled  with  blood  sub- 
jected to  considerable  pressure,  which  may  be  estimated 
at  one-fourth  of  an  atmosphere  (see  further  on).  We  can 
easily  conceive  that,  in  order  to  overcome  this  pressure,  great 
force  is  required  on  the  part  of  the  ventricle :  it  therefore 
contracts  slowly  and  with  much  force.  Contrary  to  what  we 
have  seen  in  the  case  of  the  auricle,  t?ie  ventricular  systole 
occupies  quite  an  appreciable  space  of  time.  It  is  for  this 
reason,  also,  that  the  walls  of  the  ventricles  are  much  thicker 
than  those  of  the  auricles,  and  in  proportion  to  the  resist- 
ance there  is  to  be  overcome,  those  of  the  left  ventricle  being 
thicker  than  those  of  the  right. 

Thus  the  pulmonary  artery  (or  aorta,  left  ventricle)  is 
forced  to  receive  the  blood  which  the  ventricle  pours  into  it. 
The  ventricle  is  completely  emptied:  its  contraction  is  no 
longer  necessary,  and  it  is  relaxed ;  it  is  now  that  the  heart 
is  still.  We  represented  the  total  duration  of  a  cardiac  rev- 
olution hyfive:  the  first  fifth  being  occupied  by  the  contrac- 

^  This  theory  has  lately  furnished  a  lively  discussion  in  the 
Acad6mie  de  Medecine  (Gaz.  Hebd.,  10  Avril,  1874). 


138  THE  BLOOD  AND  ITS   CIRCULATION. 

tioii  of  the  auricle  (one-fifth) ;  the  three  following  fifths,  by 
the  contraction  of  the  ventricle  (three-fifths) ;  in  the  last 
fifth,  the  heart  being  in  entire  repose  (see  the  table,  p.  141). 
We  know  that  during  these  four  latter  fifths  (three-fifths  of 
ventricular  systole  and  one-fifth  of  total  repose)  the  auricle 
is  quite  still.  Speaking  generally,  the  revolution  of  the  heart 
is  divided  into  three  periods :  the  first,  of  auricular  systole ; 
the  second,  of  ventricular  systole;  the  last,  of  entire  repose. 
The  typical  length  which  we  have  assigned  to  these  three 
periods  may  vary  greatly,  according  to  circumstances  and 
individuals,  and  even  in  animals :  the  second  period,  that  of 
repose,  presents  the  greatest  number  of  varieties :  among  the 
cold-blooded  animals,  the  batrachians  particularly,  there  is  a 
long  interval  of  repose  after  each  contraction  of  the  heart. 

But  why,  when  the  heart  is  in  repose,  does  not  the  blood 
which  has  been  driven  into  the  artery  return  to  the  ventricu- 
lar cavity  ?  Because  the  arterial  orifice  (pulmonary  or  aortic) 
is  furnished  with  three  semilunar  or  sigmoidal  valves,  which 
are  thrown  out  by  the  retrograde  pressure  of  the  blood,  and 
completely  close  the  corresponding  orifice.  There  is  no  need 
of  a  lengthened  explanation  of  this  mechanism,,  which  is 
plain  to  any  one  who  will  dissect  a  heart.  At  the  moment 
when  the  blood  has  a  tendency  to  flow  back  again,  the  fob- 
like form  of  these  valves,  the  orifice  of  which  is  turned 
towards  the  arterial  cavity,  presents  a  sort  of  trap  to  the 
blood,  by  which  the  valves  are  forced  out,  and  thus  occlude 
the  passage.  The  nodule  of  Arentius,  which  is  placed  in 
the  middle  of  the  free  edge  of  each  of  these  valves,  has,  no 
doubt,  the  eflfect  of  making  the  occlusion  more  complete. 

To  sum  up :  — 

1.  The  auricle  contracts  instantaneously  and  without  much 
force,  that  it  may  throw  the  blood  into  the  ventricle,  which  is 
only  too  ready  to  receive  it.  At  all  other  times  the  auricle  is  in 
a  state  of  relaxation,  of  slow  and  progressive  distention,  which 
produces  the  effect  of  blood-letting  at  the  terminal  extremity 
of  the  venous  system. 

2.  The  ventricle  contracts  strongly  and  slowly,  on  account 
of  the  resistance  which  it  has  to  overcome,  and  which  is 
occasioned  by  the  tension  of  the  blood  by  previous  contrac- 
tions accumulated  in  the  arteries. 

The  auriculo-ventricular  valves  are  not  valves,  but  an  en- 
tirely distinct  apparatus. 

The  semilunar  valves  are  true  valves. 

/Sounds  and  Impulse  of  the  Heart.  —  Hitherto  we  have 


CIRCULATION.  — THE  HEART,  139 

made  use  indifferently  of  the  words  "  right "  or  "  left  heart," 
"aorta"  or  "pulmonary  artery,"  because  all  that  is  said  of 
the  right  heart  applies  equally  to  the  left,  and  there  are  no 
more  valves  in  the  pulmonary  veins  than  in  the  vena  cava. 

The  phenomena  which  we  have  examined  in  the  two  hearts 
are  manifested  outwardly  by  particular  sounds  {first  atid 
second  sound  of  the  heart)  and  by  the  impulse  or  shock  of 
the  heart ;  there  are  one  impulse  and  two  sounds  to  every 
cardiac  revolution. 

The  impulse  of  the  heart  (or  shock)  consists  in  a  tremor 
which  we  feel  against  the  walls  of  the  thorax :  by  placing 
the  hand  upon  the  sixth  rib,  to  the  right  of  the  nipple,  we 
feel  that  the  heart  seems,  as  it  were,  thrown  at  each  contrac- 
tion against  the  side,  like  a  hammer  upon  an  anvil.  But 
there  is  really  no  blow,  in  the  proper  sense  of  the  word, 
because  the  point  of  the  heart  always  touches  the  wall  of 
the  thorax,  and  there  is  never  any  separation  between  them. 
Indeed,  such  a  separation  is  inconceivable,  there  being  noth- 
ing to  fill  the  void  which  it  would  occasion,  nothing  to  inter- 
pose between  the  heart  and  the  thorax,  not  even  the  lung, 
for  there  are,  in  general,  four  pulsations  of  the  heart  to  one 
expansion  of  the  lung.  There  is  thus,  at  each  apparent 
shock,  only  a  more  decided  contact  between  the  heart  and 
the  corresponding  part  of  the  chest  wall.  Many  theories 
have  been  adduced  to  explain  this  phenomenon,  the  most 
generally  received  of  which  is  that  of  Hiffelsheim,  theory  of 
recoil  (du  choc  en  retour).  The  shock,  received  by  the  heart 
at  the  instant  that  the  contents  of  the  ventricle  are  expelled, 
is  compared  to  the  recoil  of  a  gun  when  it  is  fired.  But  this 
shock  is  felt  on  whatever  side  the  heart  is  touched,  even  at 
its  lowest  part  through  the  diaphragm ;  this  simple  experi- 
ment refutes  the  theory  of  recoil,  as  not  being  always  appli- 
cable ;  and  also  overthrows  that  which  is  founded  on  the 
straightening  of  the  arch  of  the  aorta,  under  the  influence 
of  the  flow  of  blood,  the  more  so  because  this  shock  to  the 
heart  takes  place  even  in  animals  which  have  no  arch  to  the 
aorta. 

The  movement  of  the  heart  may  be  best  described  by  re- 
membering the  changes  in  fonii  and  consistency  which  the 
ventricle  undergoes  at  the  moment  when  the  systole  takes 
place :  it  passes  from  a  state  of  relaxation  into  one  of  con- 
traction, and  presses  strongly  upon  its  contents  in  such  a 
manner  as  to  force  them  into  the  arterial  tree,  which  already 
contains  blood  under  tolerably  strong  tension.     Even  if  the 


140  THE  BLOOD  AND  ITS  CIRCULATION. 

thorax  of  an  animal  be  opened,  and  the  heart  taken  out  with 
the  hand,  this  change  of  consistency,  coinciding  with  the 
ventricular  systole,  may  be  felt  over  the  whole  surface :  the 
pulsation  of  the  heart  is  then  felt,  as  when  the  hand,  placed 
over  the  cardiac  region,  feels  it  through  the  wall  of  the  chest. 
The  displacement^  the  recoil,  and  even  the  torsion  of  the 
heart  thus  have  little  to  do  with  producing  the  shock  felt ;  it 
is  principally  owing  to  the  change  in  the  condition  of  the 
ventricle,  which,  at  first  flabby  and  soft,  stiffens  throughout 
in  order  to  expel  its  contents. 

In  the  auscultation  of  the  heart  we  hear,  during  one  of  its 
contractions,  two  sounds  succeeding  each  other  at  short  inter- 
vals. It  has  been  demonstrated  by  a  long  series  of  vivisec- 
tions that  the  ^rs^  sownc?  is  produced  during  the  systole  of 
the  ventricle,  and  the  second  immediately  after  the  systole, 
when  the  heart  enters  a  state  of  complete  repose.  We  are 
agreed  as  to  the  explanation  of  the  second  sound:  as  it  is 
produced  during  the  repose  of  the  heart,  it  is  evidently  not 
caused  by  any  movement  in  that  organ.  It  is,  therefore,  in 
general,  rightly  attributed  to  the  movements  of  the  aortic 
and  pulmonary  (semilunar)  valves,  which  stiffen  suddenly  in 
arresting  the  backward  flow  of  the  blood.  This  sound  is 
short  and  sharp  (theoiy  of  Rouanet). 

It  is  more  difficult  to  explain  ihe  first  sound.  It  is  gener- 
ally supposed  to  be  owing  to  the  play  of  the  auriculo-ventri- 
cular  valves ;  but  if  these  membranous  folds  really  act  as 
valves,  they  ought  to  stiffen  suddenly ;  and  as,  moreover, 
the  first  sound  lasts  a  certain  time,  nearly  corresponding 
with  that  of  the  contraction  of  the  ventricle,  its  intensity 
and  its  length  can  only  be  explained  by  supposing  it  to  be 
caused  by  the  muscular  contraction  of  the  walls  of  the  ven- 
tricle. If,  on  the  other  hand,  we  call  to  mind  the  description 
given  of  the  working  of  the  auriculo-ventricular  apparatus, 
and  take  into  account  the  resemblance  of  this  sound  to  that 
of  a  sail  flapping  in  the  wind,  or  of  a  towel  suddenly  taut- 
ened when  stretched  out  by  the  four  corners,  its  explanation 
becomes  simple.  It  is  a  sonorous  manifestation  of  the  work- 
ing of  the  membranous  auriculo-ventricular  sails,  stretched 
out  by  the  papillary  muscles  and  their  tendons,  as  long  as 
the  ventricular  systole  lasts.  These  long,  jerky,  and  ener- 
getic tensions  are  exactly  what  would  produce  the  sound 
which  we  have  described. 

In  order  to  sum  up  the  relative  length  of  the  auricular  and 
ventricular  systoles  and  diastoles,  we  will,  with  a  line  divided 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.    141 

into  five  parts  representing  the  length  of  a  cardiac  revela- 
tion, register,  as  follows,  the  time  of  each  of  these  movements 
and  of  the  corresponding  sounds :  — 


Auricle. 
Ventricle. 
Sounds. 
Shock. 


Systole. 
Ilepose. 


Silence. 


Diastole  or  repose, 
Systole. 


1st  Sound. 
Impulse. 


2d  Sound. 


Fig.  40. 
Diagram  of  a  vascular  cone.* 


II.   Peripheric  Organs  of  the  Circulation. 

A.  Mechanical  arrangement  of  these  organs. 

We  have  seen  that  there  is  an  artery  which  begins  in  the 
ventricle,  and  becomes,  as  it  continues,  more  and  more  rami- 
fied (A).  In  a  mechanical  or  hydrostatic  point  of  view  we 
may  leave  out  of  consideration 
the  ramified  form  of  the  arterial 
tree  (Fig.  40) ;  that  is,  in  plac- 
ing all  the  arterial  trunks  (B) 
in  juxtaposition,  we  need  not 
take  into  account  all  the  parti- 
tions which  result  from  placing 
the  vessels  side  by  side  (C). 
Now,  as  it  is  proved  that  when 
a  vascular  trunk  is  divided,  the  sum  of  the  containing  space 
in  the  two  branches  is  always  greater  than  that  of  the  prim- 
itive trunk ;  so  that  the  capacity  of  the  system  increases  the 
farther  it  is  removed  from  the  aortic  trunk,  we  obtain,  in  the 
diagram  made  as  above  described,  a  conic  figure  of  the  arte- 
rial system  (Fig.  40  C).  This  cone  will  spread  out  like  a 
tent,  and  the  widening  will  be  considerable  at  the  arterial 
extremities  (base  of  the  cone),  because  the  bed  in  which  the 
blood  circulates  is  greatly  enlarged  as  it  approaches  the 
capillaries  (Fig.  41).  The  same  principles  being  applied  to 
the  venous  system,  the  latter  may  be  theoretically  represented 
by  a  cone  placed  with  its  base  in  opposition  to  the  cone  of 
the  aorta^  the  common  base  representing  the  capillary  system, 
and  thus  forming  a  short  cylinder  placed  between  two  cones 


♦  Construction  of  a  vascular  cone,  an  arterial  cone,  for  instance.  A,  Artenr, 
bifurcated  repeatedly.  In  B  the  bifurcated  branches  are  supposed  to  be  brought 
close  together,  giving  rise  to  a  partitioned  cavity.  In  C,  by  removing  these  par- 
titions, we  tind  that  the  whole  of  the  primitive  trunk  and*  its  divided  branches 
form  a  cone. 


145  THE  BLOOD  AND  ITS  CIRCULATION. 

(Fig.  41).     As  regards  their  relation  to  the  heart,  we  have 
seen  already  that  at  the  summit  of  the  arterial  cone  is  found 

a  muscular  reservoir,  the 
left  ventricle;  and  at  the 
summit  of  the  venous  cone 
a  similar  reservoir,  the 
right  auricle.  This  con- 
stitutes the  system  of  gen- 
eral circulation,  th£  greater 
'^k  41- -Diagram  of  the  whole  extent  of  circulation.      In   addition 

the  arterial  and  venous  cone,  with  the  in-    ^        ,  .      .,       ,  , 

terposition  of  the  capillaries.*  to  this  double  cone,  as  rep- 

resenting the  general  cir- 
culation, a  similar^ne  may  be  placed  representing  the  pul- 
monary circulation :  as  in  the  case  of  the  first-mentioned 
system,  the  two  extremities  of  this  double  cone  will  each 
communicate  with  a  muscular  reservoir ;  the  right  ventricle 
on  the  one  hand,  and  the  left  auricle  on  the  other.  By  giv- 
ing these  two  systems  of  cones  a  curved  form,  so  as  to  bring 
their  different  summits  to  the  same  central  point,  as  is  the 
case  with  the  heart  in  the  living  body,  a  graphic  description 
of  the  whole  circulatory  system  may  be  given,  under  the 
figure  of  two  incomplete  circles  joined  at  their  free  extremi- 
ties, thus  forming  a  sort  of  figure  of  8  (Fig.  42). 

This  figure  shows  plainly  that  the  four  muscular  reservoirs 
which  form  the  heart  are  so  arranged  that  the  pulmonary 
double  cone  is  in  communication  with  the  double  cone  of 
the  general  circulation.  For  this  purpose  the  left  auricle, 
communicating  with  the  system  of  the  pulmonary  veins, 
opens  into  the  left  ventricle  at  the  beginning  of  the  system 
of  the  general  circulation ;  this  is  the  left  heart.  On  the 
other  hand,  the  right  auricle,  communicating  with  the  gen- 
eral venous  system,  opens  into  the  right  ventricle  at  the 
point  of  departure  of  the  pulmonary  arterial  cone ;  this  is 
the  right  heart. 

Knowing  the  mechanism  of  the  heart,  we  can,  by  means 
of  this  simple  sketch  or  diagram  of  the  peripheral  organs, 
account  for  the  circulation^  and  determine  the  two  essential 
conditions  of  the  blood  when  in  motion;  these  are  \l^ pres- 
sure and  its  velocity  in  the  different  parts  of  the  circulatory 
apparatus. 

Pressure.  —  At  each  contraction  the  ventricle  pours  from 

*  V,  Ventricle.  O,  Auricle,  a,  Arterial  cone,  r,  Venous  cone,  c,  c,  Capil- 
laries. 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.    143 


180  to  200  grammes  of  blood  into  the  system  of  the  arterial 
cone,  the  effect  of  which  is  to  maintain  in  it  a  pressure  equal 


to  one-fourth  or 
the  atmosphere. 


one-fifth  of  the  weight  of 
The  auricle,  on  the  con- 


Pig.  42.  —  Diagram  ol 
tlie  greater  and  lea- 
ser circulation.* 


trary,  being  placed  at  the  summit  of  the 
venous  cone,  has  the  effect,  by  its  relaxa- 
tion, of  diminishing  the  pressure  and  nulli- 
fying it  at  the  extremity  of  the  cone ;  we 
have,  indeed,  already  compared  its  effect  to 
that  produced  by  blood-letting.  There  re- 
sults a  gradual  lessening  of  the  pressure  in 
the  interior  of  the  hydrostatic  apparatus 
formed  by  the  two  cones ;  this  diminution  of 
pressure  causes  the  blood  to  circulate  from 
the  left  ventricle  to  the  right  auricle :  in 
other  words,  the  want  of  equilibrium  gives 
rise  to  a  constant  current  towards  the  point 
where  the  pressure  is  feeblest. 

The  pressure  of  the  blood,  at  any  point 
of  the  circulatory  apparatus,  corresponds  to 
the  distance  at  which  this  point  is  placed  from  the  ventricu- 
lar and  the  auricular  summit  of  the  double  circulatory  cone : 
the  pressure  is  greatest  {\  or  ^^^  of  the  atmosphere)  at  the 
level  of  the  ventricular  summit,  that  is,  in  the  aorta;  in  the 
auricular  summit,  that  is,  in  the  vena  cava,  it  may  be  said  to 
be  0  (or  yj^)  of  the  atmosphere.  It  will  thus  be  -^^  in  the 
capillaries,  which  are  placed  half-way  between  these  twQ 
extremities.  At  any  other  point  in  the  arteries  it  may  be 
represented  by  any  number  between  -^^  and  .^^,  according 
to  the  position  of  the  point  under  consideration,  and  the  case 
is  the  same  with  regard  to  the  venous  cone.  Thus,  when  an 
artery  is  opened,  especially  near  its  beginning,  a  jet  of  blood 
is  seen  which  rises  to  a  great  height  (as  much  as  two  meters); 
while  from  an  opening  made  in  the  veins  the  blood  only 
drops,  unless  artificial  pressure  is  applied,  as,  for  instance,  by 
placing  a  ligature  on  the  veins  (as  is  done  before  bleeding 
the  arm). 


*  A,  Greater  circulation.  V,  Left  ventricle,  a^  Aorta  and  its  arterial  cone, 
c,  c,  Capillaries  of  the  body  in  general,  t;,  Veins  which  go  to  form  the  vena  cava 
(venous  cone).    0,  Right  auricle. 

Bj  Lesser  circulation.  V,  Right  ventricle,  t/,  Pulmonary  artery,  with  its 
divisions  (arfeHaf  cone  of  the  lesser  circulation),  c',  </,  Pulmonary  capillaries, 
a'  Pulmonary  veins  {vetious  cone  of  the  lesser  circulation).  C,  Left  auricle. 
(Tlie  shaded  part  of  the  figure  represents  that  part  of  the  vascular  system  which 
is  filled  with  blood  from  the  veins.) 


144 


THE  BLOOD  AND  ITS  CIRCULATION. 


These  differences  in  the  lateral  pressure  effected  by  the 
blood  upon  the  walls  of  the  vessels  through  which  it  passes 

imay  be  more  correctly  ascer- 
tained by  placing  different 
parts  of  the  circulatory  sys- 
tem in  communication  with 
a  manometric  apparatus, 
called,  when  applied  to  this 
special  use,  a  hemodynamo- 
mei&r.  The  first  hemodyna- 
mometer,  employed  by  Hales, 
consisted  of  a  long  tube, 
which  this  physiologist  in- 
troduced into  a  vessel,  and 
in  which  the  blood  rose  to  a 
height  proportioned  to  the 
pressure.  This  instrument 
has  been  greatly  improved, 
and  a  mercurial  manometer 
is  now  employed,  in  which, 
in  order  to  avoid  the  coagu- 
lation of  the  blood,  the  col- 
umn of  blood  is  separated 
from  the  mercury  by  a  col- 
umn of  some  alkaline  solu- 
tion (solution  of  carbonate 
of  soda),  which  prevents  the 
too  speedy  consolidation  of 
the  fibrine  (Fig.  43). 

The  pressure  of  the  at- 
mosphere for  the  larger  arte- 
ries has  thus  been  found  to 
be  about  one-fourth;  for  those  which  are  farther  from  the 
heart,  as  the  humeral  artery,  one-sixth,  and  so  on.     In  the 

*  This  instrument  consists  of  a  thick,  heavy  glass  bottle.  At  T  is  a  tube, 
open  at  one  end :  the  other  extremity  of  the  tube  leaves  the  bottle,  and  is  bent 
upwards,  receiving  at  «  a  graduated  glass  tube  (T).  The  lower  part  of  the  bottle 
and  the  beginning  of  the  graduated  tube  are  filled  with  mercury. 

The  upper  part  of  the  bottle  is  closed  by  a  stopper  containing'a  tube  (*),  which 
is  joined  to  a  metal  tube  c.  The  latter  passes  into  the  vessel  in  which  the  pres- 
sure is  to  be  measured. 

When  the  instrument  is  in  action  the  whole  upper  part  of  the  apparatus  C,  c,  <, 
is  filled  with  a  solution  of  bicarbonate  of  soda,  in  order  to  prevent  the  coagula- 
tion of  the  blood.  The  pressure  effected  by  the  blood  upon  the  surface  of  the 
mercury  is  communicated  through  the  opening  T  to  the  mercury  in  the  gradu- 
ated tube,  and  by  this  means  the  tension  of  the  blood  is  measured. 

This  instrument  (Magendie's  cardiometer)  has,  over  the  manometers  usually 


Fig.  43.  —  HemodjTiamometer  (or  car- 
diometer).* 


r 


PERIPHERIC  ORGANS  OF  THE  CIRCULATION.    145 


veins,  on  the  contrary,  the  pressure  is  found  to  be  ex- 
tremely feeble,  as  an  examination  of  the  above  diagrams  has 
shown.  The  pressure  in  the  capillaries  cannot  be  measured 
exactly :  it  is,  probably,  as  we  have  said,  ^^  of  the  atmos- 
phere. In  hemorrhage  from  the  capillaries,  however,  the  blood 
does  not  come  out  in  jets :  its  flow  is  here  greatly  retarded 
by  the  friction  which  it  undergoes  against  the  walls  of  these 
small  tubes.  If  we  examine  the  circulation  of  the  capillaries 
with  a  microscope,  we  shall  see  that  all  the  external  portions 
of  the  blood  current  as  it  flows  adhere  to  the  walls  of  the 
vessels,  almost  without  motion  (passive  layer) ;  the  central 
column  alone  moves,  drawing  with  it  the  globular  elements 
of  the  blood,  especially  the  red  globules ;  for 
the  white  globules,  which  are  extremely 
viscous,  are  easily  caught,  and  arrested  in  the 
passive  layer  (Fig.  44). 

These  ideas  as  to  the  distribution  of  pres- 
sure in  the  circulatory  system,  though  so  sim- 
ple, were  not  easily  acquired.  Poiseuille  at 
first  maintained  that  the  pressure  was  the 
same  at  all  points  of  the  circulatory  system, 
at  whatever  distance  from  the  ventricle.  This 
view,  which  reason  alone  might  have  shown  to 
be  an  error,  was  experimentally  overthrown  by 
Marey ;  who  has  demonstrated  that  in  the  vas- 
cular system,  from  the  heart  to  the  capillaries, 
the  pressure  is  distributed  as  in  a  liquid  placed 
in  a  tube  with  one  end  open,  and  the  other 
communicating  with  the  bottom  of  a  vase  filled 
with  liquid  at  a  certain  pressure.  Poiseuille  had  also  imag- 
ined that  the  general  pressure  varied  in  animals  of  diff*erent 
bulk,  and  always  in  proportion  to  their  size.  But  Claude 
Bernard  has  demonstrated  that  this  is  not  at  all  the  case  since 
the  same  apparatus  with  which  we  measure  the  mean  or  mini- 
mum pressure  in  a  rabbit  is  quite  sufficient  to  measure  the 
same  pressure  in  a  horse.  But,  by  means  of  the  cardiometer, 
he  has  also  shown  that  two  things  must  be  distinguished  in  the 

employed  (Poiseuille  and  Ludwig's  instruments),  this  advantage,  that  it  records 
exactly  the  cardiac  pulsations ;  because  the  mercury,  in  this  case,  fills  a  compara- 
tivel}'  large  bottle,  and  not  simply  a  tube  in  the  shape  of  a  U ;  and  the  whole 
mass  of  the  mercury  is  not  displaced  at  every  change  of  pressure  ;  neither  does 
that  friction  take  place  wliich  produces  the  loss  of  a  large  part  of  the  force  to  be 
measured. 

*  r,  Central  cun-ent  of  the  red  globules.     Z,  /,  h  Peripheral  layer  of  the  blood 
current,  in  which  the  white  globules  move  more  slowly.     (280  diam.) 

ID 


Pig.  44— Capillary 
vessel  of  the  in- 
terdigital  mem- 
brane of  a  frog.* 


146  THE  BLOOD  AND  ITS  CIRCULATION. 

pressure  of  the  arterial  system :  1,  What  we  have  called  gen- 
eral pressure,  minimum  pressure ;  2,  The  oscillations  which 
this  pressure  undergoes  at  every  fresh  projection  of  blood 
from  the  ventricle.  By  the  appreciation  of  this  new  element, 
these  rhythmic  maxima^  Poiseuille's  idea  is  justified  up  to  a 
certain  point :  —  the  pressure  varies  in  different  animals  owing 
to  a  variety  of  causes,  among  which  size  holds  no  unimport- 
ant place  (CI.  Bernard). 

Velocity,  —  The  velocity  and  the  pressure  of  the  blood  at 
any  given  point  do  not  always  exactly  correspond :  we  have 
seen  that  by  stopping  the  flow  of  blood  in  a  vein  we  increase 
the  pressure.  The  pressure  at  any  given  point  depends  on 
the  distance  of  this  point  from  the  extremities  of  the  double 
circulatory  cone ;  while  the  velocity,  on  the  contrary,  depends 
on  the  form  and  width  of  that  part  of  the  circulatory  cones  in 
which  the  point  is  situated.  In  other  words,  and  this  is  easily 
understood,  the  rapidity  of  the  movement  of  the  blood  is  in 
proportion  to  the  space  contained  in  that  part  of  the  tube  under 
consideration.  It  must  be  remembered  that  we  always  speak 
of  the  united  tubes  under  the  appellation  of  the  double  cone. 
Thus,  where  the  circulatory  system  is  very  large,  as  at  the 
base  of  the  cones  (the  region  of  the  capillaries),  the  blood  cir- 
culates slowly ;  exactly  as  the  current  of  a  river  slackens 
greatly  as  the  river  widens,  —  into  a  lake,  for  instance:  tlms 
the  capillaries  form  the  lake  of  the  hloodr-torrent.  The  max- 
imum of  the  velocity  is,  however,  attained  in  the  narrow 
orifices  through  which  the  blood  flows,  that  is,  towards  the 
summit  of  the  cones  in  the  aorta  and  in  the  vena  cava. 

These  conclusions  have  been  verified  by  direct  experiment. 
The  speed  in  the  capillaries  has  been  measured  by  microscopic 
examination  of  the  small  vessels  of  the  frog,  for  instance ;  or 
by  examining  with  the  ophthalmoscope  the  capillaries  in  the 
retina  of  man ;  wherein  the  blood  globules  can  be  distinctly 
traced,  and  the  time  necessary  for  them  to  traverse  a  given 
distance  calculated ;  it  has  thus  been  decided  that  the  speed 
in  the  capillaries  is  only  from  one-half  to  one  millimetre  a 
second.  This  is  trifling,  compared  with  what  we  shall  find 
in  the  larger  vessels,  but  we  mu§t  bear  in  mind,  not  only  that 
the  capillary  system,  taken  altogether,  forms  the  lake  of  the 
hloodr-torrent^  but  also  that  this  lake  is  subdivided  into  a  mass 
of  fine  net-work,  friction  against  which  deprives  the  liquid 
of  much  of  its  impulsive  force.  The  influence  of  this  fric- 
tion, of  this  adherence  to  the  walls  of  the  capillaries,  is  fully 
shown  by  the  researches  of  Poiseuille  on  the  flow  of  the 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.     147 


liquids  through  tubes  having  a  small  diameter.  They  may- 
be summed  up  in  the  two  following  laws:  the  quantities 
flowing  are  to  each  other  as  the  fourth  power  of  the  diameters 
of  the  tubes  /  they  are  in  inverse  ratio  to  the  length  of  the 
tubes.  Now  the  capillary  vessels,  in  addition  to  their  net- 
like arrangement,  form  very  long  tubes,  and  thus  unite  all 
the  conditions  necessary  to  slacken  the  flow^  of  the  blood  and 
prolong  its  contact  with  the  tissues. 

In  order  to  estimate  the  velocity  of  the  blood  in  the  large 
vessels,  special  instruments  are  employed ;  or  else  a  glass 
tube  filled  with  an  alkaline  liquid  is 
substituted,  and  placed  at  a  certain 
point  in  an  artery  of  large  diameter, 
the  time  being  then  determined  neces- 
sary for  the  blood  to  drive  the  liquid 
in  question  from  the  tube  and  after- 
wards traverse  the  known  length  of 
this  artificial  channel.  This  appara- 
tus is  the  hemodromometer  (of  Volk- 
mann)  (Fig.  45),  and  is  composed  of 
a  glass  tube  (A),  bent  like  a  horse- 
shoe, furnished  at  each  end  with  a 
metal  spout  having  a  cock,  and  com- 
municating with  a  straight  metallic 
tube  inserted  in  the  two  ends  of  the 
artery  («,«').  The  tube  being  filled  with  the  alkaline  solu- 
tion, and  all  communication  with  the  artery  (Fig.  45,  No.  1) 
is  shut  off  by  means  of  the  cocks  (having  three  outlets) ;  this 
causes  the  blood  to  follow  the  metallic  tube ;  the  two  cocks 
are  suddenly  turned,  and  the  blood  is  thereby  forced  to  devi- 
ate from  its  course  and  enters  the  glass  tube  (Fig.  45,  No. 
2),  which  it  traverses  to  gain  the  other 
end  of  the  artery,  driving  before  it  the 
column  of  colorless  liquid.  An  apparatus 
which  is  quite  as  ingenious,  called  the 
hemotachometer  (of  Vierordt),  consists 
of  a  small  transparent  box  (Fig.  46), 
placed  in  a  portion  of  the  artery.  In  this 
box  swings  a  pendulum,  which  the  cur- 
rent of  blood  causes  to  swerve  to  one  side ; 
this  deviation  increases  with  the  rapidity 
of  the  current,  and  by  its  degree  we  can  calculate  the 
velocity  of  the  blood*  These  experiments  show  that  the 
velocity  of  the  blood  is  Om.  33  (thu-ty-three   centimetres) 


\ 


emodromometer . 


O 


:> 


^g.  46.  — Vierordfs 
Hemotachometer. 


148  THE  BLOOD  AND  ITS  CIRCULATION. 

a  second  in  the  camtid  artery,  and  Om.  44  in  the  aorta:  it  is 
also  four  hundred  times  greater  in  the  latter  vessel  than  in 
the  capillaries.  Similar  results  have  been  obtained  with 
the  hemodromometer  of  Chauveau,  and  the  hemodromo- 
grapher  of  Lortet  (Fig.  47),  which  are  constructed  on  the 
same  principle  as  Vierordt's  instrument. 

By  means  of  the  above  data  on  the  velocity  of  the  blood 
we  can  calculate  the  dimensions  of  the  arterial  cone.  Indeed, 
the  velocity  at  the  different  points  of  the  cone  are  in  inverse 
ratio  to  the  surface  of  the  section  of  the  cone  at  this  point :  the 
total  containing  space  of  the  capillary  system  is  thus  to  that  of 
the 'aorta  as  400  to  1.  We  may  therefore  conclude  that  the 
containing  space  of  the  aorta  having  a  diameter  of  3  centi- 
metres, the  diameter  of  the  base  of  the  arterial  cone  must 
be  about  Om.  66.  If  the  exact  capacity  of  this  cone  were 
known,  it  would  be  easy  to  calculate  its  height.  These  cal- 
culations, however,  yield  only  approximative  results,  for  the 
slackening  of  the  current  of  the  blood  at  the  level  of  the 
capillaries  is  also  an  important  feature,  which  is  not  here 
taken  into  account :  it  is  caused  by  the  net-like  arrangement 
of  long  and  narrow  tubes  (see  the  two  laws  of  Poiseuille, 
p.  147,  above). 

It  may  still  be  asked,  after  determining  the  velocity  of  the 
blood  in  certain  points,  what  is  the  general  speed,  considering 
the  circulation  as  a  whole?  In  one  word,  how  much  time  is 
necessary  for  a  blood  globule  to  pass  from  the  left  ventricle 
to  the  right  auricle  ?  The  average  quantity  of  blood  thrown 
into  the  aorta  at  each  contraction  of  the  heart  is  180  grammes. 
As  the  total  mass  of  the  blood  is  only  5  kilogrammes,  25  or 
80  cardiac  pulsations  are  necessary  to  enable  all  the  blood  to 
pass  through  the  central  organ,  and  rather  more  than  30 
seconds  for  the  return  of  a  globule  which  has  left  the  heart. 
The  result  of  this  calculation  can  only  be  general  and  ap- 
proximative; for  the  blood  which  goes  to  the  lower  limbs 
has  a  much  longer  passage  than  that  which  passes  into  the 
cardiac  veins  and  arteries:  the  time  of  the  complete  journey 
(going  and  returning)  of  a  blood  globule  must  therefore  vary, 
according  to  the  part  to  which  it  is  sent.  Still,  the  circula- 
tion must  always  be  extremely  rapid,  as  is  proved  by  experi- 
ment in  cases  of  poisoning;  for  we  know  that  a  drop  of 
prussic  acid  upon  the  conjunctiva  will  kill  an  animal  in  eight 
or  ten  seconds,  and  that  the  poison  is  found  to  be  diffused 
through  the  whole  system.  If  the  poison  is  placed  further 
from  the  heart,  upon  a  wound  in  the  foot,  for  instance,  death 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.       149 


I   d)  . -;  CO  ^  a> 

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«-s  S^  S^ 


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rt  2  ^  eS  eS  « 


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t-l   g-         ^    2    3    N 


^^^ 


150  THE  BLOOD  AND  ITS  CIRCULATION. 

does  not  ensue  quite  so  soon,  because  the  blood  takes  more 
time  to  return  by  the  saphenous  than  by  tlie  jugular  veins. 
The  standard  experiment  consists  in  injecting  yellow  cyanide 
into  the  central  end  of  the  jugular  vein,  and  collecting  the 
blood  which  flows  out  at  the  peripheral  end.  We  And  that, 
after  the  lapse  of  from  eight  to  fifteen  seconds,  the  poison 
appears  at  this  end,  the  blood  beginning  to  show  the  charac- 
teristic reaction  of  prussian  blue  (with  salts  of  iron). 

Special  Arrangement  of  the  Circulatory  Systetn  in  sotne 
Organs.  —  Such  are  the  general  conditions  of  the  circulation, 
of  its  pressure  and  its  velocity  at  different  points.  But  the 
system  of  cones  which  we  have  been  considering  is  not 
always  everywhere  so  simple,  and  we  find,  in  different  parts 
of  the  circulatory  apparatus,  arrangements  and  conditions 
which  are  purely  physical  and  mechanical,  and  which  mo<Ufy 
the  rapidity  of  the  course  of  the  blood.  Such  are  the  great 
number  of  tubes,  the  clusters  of  capillaries,  called  the  retia 
mirabilia,  the  type  of  which  is  an  artery  suddenly  divided 
without  altering  its  normal  or  regular  dichotomic  disposition. 
The  result  of  this  increase  at  any  one  point  of  the  capacity 
of  the  vessels  is  a  widened  cone  and  a  sudden  diminution  in 
the  rapidity  of  the  circulation  of  the  blood.  This  is  what 
takes  })lace  in  the  kidney,  as  we  shall  see  later,  at  the  level 
of  tlie  vascular  pouches,  called  the  glomerules  of  Malpighi: 
the  effect  of  this  disposition,  in  slackening  the  flow  of  the 
blood,  is  to  increase  the  surface  of  transudation;  this  trans- 
udation takes  ]dace  under  s[)ecial  conditions  of  pressure 
(Fig.  48).  We  find  something  similar  in  the  system  of  the 
venaportae:  the  blood  furnished  by  the  coeliac  axis  and  the 
mesenteries  to  the  organs  of  digestion  is  brought  back  by  a 
number  of  veins  into  a  common  trunk,  called  the  portal  vein, 
which,  instead  of  emptying  immediately  into  the  vena  cava, 
is  first  distributed  in  the  liver  in  the  same  manner  as  an 
arteiy,  and  forms  the  afferent  vessels  of  the  'liver,  the  ca- 
pillaries, and,  finally,  the  efferent  vessels,  or  hepatic  veins, 
which  flow  into  the  vena  cava.  This  whole  system  may  be 
theoretically  represented  by  a  cone  (Fig.  48)  beginning  at 
the  trunk  of  the  aorta,  and  representing  the  arteries  of  the 
intestines,  with  their  capillaries.  This  arterial  trunk  is  suc- 
ceeded by  a  venous  trunk,  showing  the  origin  and  the  trunk 
of  the  portal  vein ;  this  second  cone  is  followed  by  a  third, 
arranged  in  the  same  manner  as  an  arterial  cone  (the  circu- 
lation in  which  is  from  the  top  to  the  bottom),  and  represent- 
ing the  ramifications  of  the  portal  vein  in  the  liver ;  at  its 


r 


Diagram  of  the  double  cones  of  the 
portal  system.* 


PERIPHERIC  ORGANS  OF  THE  CIRCULATION.    151 


base  (hepatic  capillaries)  this  cone  forravS  a  fourth,  represent- 
ing tlie  hepatic  veins.  In  making  this  passage  the  blood, 
therefore,  must  traverse  a 
system  containing  twice  as 
many  cones  as  the  general 
system,  and  is  subject  at 
each  double  base  (each 
network  of  the  capillaries) 
to  the  slackening  which 
we  have  mentioned. 

The  capillary  vessels 
which  are  placed  in  the 
series  of  cones  of  the  por- 
tal vein,  moreover,  have  Fig.  48 
not  the  same  pressure  as 
the  ordinary  capillaries.  As  these  systems  are  not  placed  at 
an  equal  distance  from  the  left  ventricle  and  the  right  auri- 
cle, neither  can  have  a  pressure  hall-way  between  yj^  and 
•^^jj  of  an  atmosphere.  The  pressure  will  be  less  in  the 
hepatic  capillaries,  because  they  are  nearer  the  auricle ;  and 
greater  in  the  intestinal  capillaries,  because  they  are  nearer 
the  left  ventricle.  The  latter  condition,  as  we  shall  see,  is 
not  favorable  to  the  theory  of  intestinal  absorption  by  simple 
osmosis.  We  shall  see  also  that  the  same  theory  may  be 
asserted  with  regard  to  the  capillary  system  of  the  kidneys. 

JS.  Properties  and  functions  of  the  Vessels. 

The  general  conditions  of  the  circulation  of  the  blood,  of 
its  pressure  and  its  velocity,  which  conditions  are  simply  the 
result  of  the  mechanical  arrangement  of  the  blood  tubes, 
may  be  affected  and  complicated  by  the  physiological  prop- 
erties of  the  coats  of  the  vessels^  the  arteries^  capillaries^  and 
veins. 

Arteries.  —  Anatomy  teaches  us  that  the  arteries  are  com- 
posed of  three  coats  or  tunics  (Fig.  49).  Of  these  three  the 
most  interesting  to  the  physiologist  is  the  middle  tunic :  it 
contains  two  essential  elements,  elastic  tissue  and  muscle 

*  The  superposition  of  the  two  diagrams  shows  that  the  pressure  is  not  the 
same  in  the  capillaries  of  a  portal  system  and  in  those  of  the  circulation  m 
general. 

1,  General  circulation.  V,  Ventricle.  0,  Auricle,  a,  Arteries,  w,  Veins. 
C,  Capillaries  (pressure  12). 

2,  Portal  system.  V,  Ventricle.  0,  Auricle,  a,  Arteries.  </  c^.  First  sys- 
tem of  capillaries  (pressure  =  18).  SP,  Portal  trunk,  cc^  Second  system  of 
capillaries  (pressure  ^^  6).     v,  Vein. 


152 


THE  BLOOD  AND  ITS  CIRCULATION. 


(smooth  muscle,  contractile  cells).  The  first  of  these  ele- 
ments, elastic  tissue,  is  found,  with  slight 
exceptions  only,  at  the  summit  of  the 
arterial  cone,  the  aorta  being  formed 
almost  entirely  of  yellow  elastic  tissue. 
On  the  other  hand,  the  muscular  element 
predominates  largely  at  the  base  of  the 
cone ;  that  is,  in  the  coats  of  the  small 
arteries  which  precede  the  capillaries.  In 
the  intermediate  parts  the  elastic  and  mus- 
cular tissues  both  share  in  the  composi- 
tion of  the  middle  tunic,  in  proportion 
to  the  distance  at  which  the  point  under 
consideration  lies  between  the  base  and 
summit  of  the  cone ;  so  that  a  diagonal 
49.  —  Artery  in  li"6,  dividing  obliquely  the  thickness  of 
which  the  three  coats  the  walls  of  the  arterial  cone,  represents 

are  dissected.  ^i      ^i  ^'  •    i  •        i 

exactly  the  comparative  richness  m  elas- 
tic and  niuscular  tissue  of  the  different  parts  of  the  arterial 
walls  (Fig.  50). 


•  Arterial  cone ;  composition  of 
the  arterial  coats.* 


Fig.  51.  —Natural  form  of  the 
arteries,  t 


The  arteries  are,  owing  to  the  presence  of  the  muscular 
and  yellow  tissue,  extremely  elastic  tubes.     This  fact  alone 


♦  Proportion  of  "the  elastic  and  the  muscular  element  in  the  composition  of 
the  coat  of  the  cone  from  summit  (At)  to  base  {c,c).  1,  Muscular  element. 
2,  Elastic  element. 

t  Element  by  which  the  natural  form  of  the  arteries  is  determined.  A,  Ap- 
pearance of  the  section  of  an  artery,  supposing  it  to  be  formed  of  muscular 
tissue  only.  B,  Section  of  an  artery  supposed  to  be  of  elastic  tissue  only. 
C,  D,  Section  of  an  artery,  showing 'its  actual  ribbon-like  form,  which  is  tfie 
physiological  result  of  the*  struggle  between  these  two  elements,  the  elastic  and 
the  muscular. 


I^r  ii^di 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.     153 


indicates  that  they  have  a  natural  form,  to  wliich  they  are  con- 
stantly tending  to  return,  and  which  is  antagonized  by  the  force 
of  the  circulation.  Moreover,  they  are  not,  as  we  should  be 
likely  to  suppose,  hollow  cylinders,  but  rather  hollow  ribbons, 
with  flattened  sides.  An  artery  of  middle  size  contains  muscu- 
lar and  elastic  tissue  in  about  equal  parts.  If  there  were  only 
muscular  tissue  in  the  arteries,  as  this  is  arranged  in  circular 
layers  like  a  sphincter,  the  whole  central  opening  in  the 
artery,  on  assuming  its  natural  form  of  repose,  would  be  a 
point  or  axial  line,  serving  only  as  an  indication  of  the  canal 
(Fig.  48,  A).  The  elastic  tissue  has  a  tendency  to  keep  the 
artery  wide  open,  and,  if  this  alone  existed,  it  would  have  the 
appearance  of  a  large  cylindrical  canal  (13).  By  a  sort  of 
compromise  this  constant  antagonism  between  the  elasticity 
of  the  muscle  and  the  elastic  tissue  produces  an  intermediate 
form  between  these  two  extremes,  that  of  a  cylindrical,  flat- 
tened ribbon  (C,  or  rather  D)  slit  transversely.^ 

This  natural  form  is  constantly  opposed  by  the  mass  of 
blood  which  the  ventricle  at  each  systole  causes  to  gush  into 
the  arterial  system ;  the  arteries,  when  full  of  blood,  have 
also  the  form  of  a  cylindrical  tube ;  but  we  know,  too,  that 
they  change  their  form  according  to  the  greater  or  smaller 
quantity  of  blood  which  they  receive.  In  cases  of  severe 
hemorrhage,  they  assume  their  natural  ribbon-like  form  ; 
they  assume  it  also,  after  death,  by  ejecting  their  contents 
into  the  capillaries  and  the  veins ;  thus  th^  arteries  of  a  dead 
body  are  empty  and  flat.  We  must,  however,  add,  that  they 
preserve  this  form  in  the  dead  body,  only  when  the  air  has 
not  entered  their  interior.  Directly  any  opening  is  made  in 
their  coats,  they  begin  to  draw  in  the  air,  and  to  assume  the 
a})pearance  of  hollow  cylinders.  This  fact  is  easily  explained : 
after  the  last  pulsation  of  the  heart,  the  arteries  still  endowed 
with  their  vital  activity  have,  by  ejecting  their  content  into 
the  veins,  taken  the  natural  form  of  a  hollow,  flattened  rib- 
bon, which  form  is  due  to  the  antagonism  between  the  muscu- 
lar and  elastic  tissue;  the  muscular  tissue,  however, soon  loses 
its  properties,  and  from  that  moment,  in  a  physiological  point 
of  view,  the  artery  is  composed  only  of  elastic  tissue,  the 
natural  form  of  the  artery  of  a  dead  body  being  consequently 

*  See  Louis  Oger,  "  Considerations  Physiologiques  sur  la  Forme 
Naturelle  et  la  Forme  Apparente  de  quelques  Organes,  et  en  particulier 
sur  la  Forme  Nalurelle  et  la  Forme  Apparente  des  Arth'es.^'  These 
de  Strasbourg,  1870,  No.  26d. 


154  THE  BLOOD  AND  ITS   CIRCULATION. 

that  of  a  hollow  cylinder ;  the  pressure  of  the  atmosphere, 
however,  prevents  it  from  dilating  and  assuming  this  form, 
and  it  can  only  completely  assume  it  when  the  air  is  admitted 
into  its  cavity  by  an  incision. 

Thus,  during  life,  the  arteries  are  in  a  state  of  permanent 
tension :  this  constitutes  their  tonicity,  and  is  similar  to  what 
we  have  already  studied  in  the  s|)hincters,  and  in  the  mus- 
cles in  generaL^  The  effect  of  this  peculiar  condition  is  that 
the  arteries  do  not  serve  simply  to  conduct  the  blood  ;  they 
transform  the  circulation,  changing  the  intermittent  stream 
of  blood  which  gushes  from  the  heart,  into  a  continuous  flow. 
In  the  large  arteries  near  the  heart,  the  flow  of  the  blood  is  still 
intermittent,  but  as  we  proceed  farther  into  the  arterial  sys- 
tem, we  find  that  it  becomes  continuous.  Indeed,  by  de- 
ducing from  the  flow  of  the  carotid  artery  that  of  the 
origin  of  the  aorta,  it  has  been  calculated  that  each  blood 
wave  contains  about  180  grammes  of  blood.     This  enormous 

1  These  considerations  as  to  the  natural  and  the  apparent  form 
of  an  organ,  of  a  simple  tissue,  or  one  composed  of  several  ele- 
ments, are  of  the  highest  interest  in  general  physiology,  and 
throw  sometimes  unexpected  light  upon  the  explanation  of  certain 
phenomena.  We  have  already  studied  the  muscle  under  two  phy- 
siological forms  (form  No.  1  and  No.  2)  which  they  scarcely  ever 
perfectly  attain.  There  are  certain  ligaments,  as  the  yellow  liga- 
ments of  the  vertebral  column,  which,  also,  scarcely  ever  attain 
their  natural  form.  If  the  series  of  spinous  processes  and  laminse 
be  divided  from  the  series  of  the  articulating  masses  by  two  strokes 
of  a  saw  behind  and  throughout  the  length  of  the  vertebral  laminse, 
and  after  this  separation  the  length  of  the  two  vertical  halves  of  the 
column  be  compared,  we  shall  find  that  the  back  part  has  shortened 
in  a  very  remarkable  manner,  the  shortening  corresponding  nearly 
with  the  height  of  three  vertebrae  of  medium  size.  The  yellow 
ligaments  are  evidently  the  cause  of  this  shortening;  they  are  re- 
strained by  the  separation  and  the  rigidity  of  the  laminse  upon 
which  they  are  stretched,  which  prevents  their  assuming  their 
natural  form,  and  they  can  return  to  it  only  on  the  withdrawal  of 
this  antagonistic  force. 

We  shall  see  that  the  natural  form  of  the  lung  in  the  living  body 
differs  from  the  natural  form  of  the  lung  in  the  dead  body,  and 
that  in  the  living  and  normal  organism  the  first  is  never  found 
perfectly  developed.  This  study  will  help  us  to  comprehend  easily 
the  mechanism  of  expiration. 

By  the  natural  form,  either  of  a  tissue  or  an  organ,  must  be  under- 
stood the  form  peculiar  to  the  tissue  or  organ,  independent  of  all  foreign 
influences,  more  or  less  constant,  which  have  a  tendency  to  antagonize 
or  oppose  its  peculiar  form. 


PERIPHERIC  ORGANS  OF  THE  CIRCULATION.     155 

quantity  of  blood  must  produce  great  dilatation  of  the  aorta, 
the  coats  of  which,  reacting  in  their  turn  on  the  blood, 
drive  it  into  the  arterial  cone,  where,  by  a  series  of  dilatations 
and  successive  Avindings,  becoming  less  and  less  sensible,  the 
flow  of  the  blood  which,  in  the  summit  of  the  cone,  was 
jerky^  becomes  nearly  regular  in  the  region  of  the  capillaries 
(base  of  the  cone). 

There  is,  thus,  at  the  summit  of  the  arterial  cone,  at  each 
systole  of  the  ventricle,  a  very  sensible  wave^  which  is  still 
felt  in  the  lesser  arteries,  and  disappears  in  the  capillaries. 
This  phenomenon  constitutes  the  pulse.  The  pulsative  wave 
is  very  sensible  to  the  touch  in  the  radial  artery ;  the  pulse 
is  thus  the  impression  made  upon  the  finger  (sense  of  touch) 
by  the  approach  of  a  wave.^  A  physician  often  produces,  in 
fluids,  phenomena  exactly  similar  to  that  of  the  pulse,  such 
as  the  fluctuation  observed  as  the  result  from  a  sudden  blow 
upon  a  pouch  or  bag  filled  with  liquid ;  the  heart  produces  a 
real  percussion  on  the  mass  of  the  blood,  by  the  shock  of  its 
systolic  expulsion  ;  the  pulse,  therefore,  coincides  with  the 
beating  of  the  heart,  but  follows  it  at  a  short  interval ;  which 
is,  for  the  radial  pulse,  one-seventh  of  a  second,  the  time  nec- 
essary for  the  wave  to  flow  from  the  heart  to  the  radial  artery 
at  the  level  of  the  wrist. 

Under  certain  circumstances  the  pulsative  wave  is  trans- 
mitted more  or  less  strongly  and  rapidly,  according  as  the 
arterial  coats  are  more  or  less  stretched  out.  If  the  coat  be 
soft,  the  pulsation  is  transmitted  slowly ;  and  rapidly,  if  the 
coat,  on  the  contrary,  be  hard  ^nd  resisting.  Thus  a  stone 
falling  into  the  water  produces  waves  more  slowly  in  propor- 
tion to  the  depth  of  the  water ;  if  the  water  be  covered  with 
a  layer  of  ice,  the  propagation  of  the  waves  will  be  more 
rapid.  As  the  phenomena  of  JluctuatioUy  ohser\ed  in  sur- 
gery, are  more  or  less  distinct,  according  as  the  coats  of  the 
pouch  containing  the  liquid  are  more  or  less  stretched  (in  a 
bladder  which  is  too  much  distended,  the  flow  of  the  blood 
can  hardly  be  detected),  so  the  state  of  the  physiological 
coat  (of  the  arteries),  and  especially  the  state  of  the  arterial 
muscle,  influences  the  form  of  the  pulse.  We  know  that, 
owing  to  the  elasticity  of  this  element,  the  arteries  are  not 
rigid,  and  this  circumstance,  while  allowing  the  presence  of 
the  wave  to  be  felt,  finally  exhausts  it.     (See  above,  that 

*  Uncla   non   est   materia  progrediens,   sed  forma   materice  pro- 
grediens. 


156 


THE  BLOOD  AND  ITS   CIRCULATION. 


the  elasticity  changes  the  jerky  movement  of  the  blood  into 
a  regular  movement) ;  but  if  the  muscle  is  paralyzed,  and 
thus  has  lost  its  perfect  elasticity,  the  gradual  transformation 
of  the  intermittent  shock  into  a  continuous  movement  ceases; 
and  we  find  that  jerks  occur  in  the  smallest  arteries,  and 
even  in  the  capillaries,  as  has  been  observed  in  the  mesentery 
of  the  frog ;  the  same  takes  place  in  inflamed  tissue,  and 
there  are  few  persons  who  have  not  experienced  the  arterial, 
or  rather  capillary  pulsations  of  a  whitlow. 

In  all  this,  the  pulsation,  the  arrival  of  a  wave,  must  not 
be  confounded  with  the  movement  of  the  circulation  of  the 
blood  itself;  we  cannot  repeat  too  often,  —  unda  non  est 
materia  progrediens^  sed  forma  materim  progrediens  :  Czer- 
mak  has  proved,  by  very  close  examination  {sphymographe 
a  miroir),  that,  while  the  rapidity  of  the  movement  of  the 
blood  diminishes  as  we  approach  the  capillaries  (see  page 
132,  above),  the  speed  with  which  the  pulsative  wave  is 
propagated  increases,  on  the  contrary,  from  the  centre  to  the 
periphery,  and  that  it  is  greater  in  aged  persons  and  in 
adults  than  in  children,  showing  that  we  must  not  confound 
the  pulse,  its  rapidity  and  form,  with  the  rapidity  of  the 
blood  and  the  activity  of  its  circulation.  Onimus,  in  his 
Etudes  sur  les  traces  obtenus  par  le  sphygmograplie  (Journal 
d'Anatomie,  1866),  has  dwelt  especially  on  these  features  of 
the  pulsative  wave. 

The  waves  of  the  blood  column  may  be  ascertained  by 
placing  a  manometer  in  communication  with  the  vessel: 
alternate  rising  and  falling  is  then 
easily  observed.  Eflbrts  have  been 
made  to  count  these  undulations  by 
means  of  Ludwig's  hymographion 
(Fig.  52),  which  is  only  a  modifica- 
tion of  the  hemodynamometer  de- 
scribed above.  On  the  surface  of 
the  mercurial  column  of  the  manom- 
eter (in  a.  Fig.  52)  is  placed  a  small 
float,  having  on  its  upper  face  a  ver- 
tical stem  (6),  articulating  with  a 
second  horizontal  stem  (c),  furnished 
■r  :,_,  .  T^-  !-•  with  a  point,  which  touches  a  turninfj 

Lndwig'sKymograpiuon.    ^  ^yU^^er  (D  D')  blackened  by  smoke. 

If  this  cylinder  were  immovable,  the  style  would  trace  ver- 
tical lines;  but,  as  it  turns  regularly,  the  lines  traced  are 
undulating,  and,  according  as  their  convexity  is  in  an  up- 


d<±> 


PERIPBERIC  ORGANS  OF  TEE  CIRCULATION.    157 

ward  or  downward  direction,  they  are  called  positive  or 
negative,  the  former  corresponding  to  the  ventricular  systoles, 
and  the  latter  to  the  repose  of  the  heart. 

The  sphygmograph  of  Marey,  applied  to  the  radial  artery  in 
man,  gives  similar  results.  This  is  a  registering  apparatus, 
noting  down  the  impulsions  of  the  artery  imprinted  upon  it : 
this  is  done  by  means  of  a  small  lever,  applied  to  the  artery 
in  the  same  manner  as  the  finger  of  a  physician  when  examin- 
ing the  pulse.  The  comparative  duration  of  the  systole  and 
the  diastole  is  decided  by  the  length  of  one  of  these  waves, 
as  may  also  all  the  modifications  of  the  circulation  (Fig.  53). 
It  has  thus  been  shown  that  the  dicrotism  of  the  pulse, 
plainly  sensible  to  the  touch  in  some  diseases,  is  only  the 
exaggeration  of  a  dicrotism  constantly  taking  place  in  the 
normal  condition  of  the  blood  wave.  It  consists  in  a  slight 
elevation,  seen  in  the  line  of  descent  in  the  diagram  (Fig. 
53,  in  d),  and  is  a  sort  of  second  pulsation  coming  after  the 
first.    The  investigations  of  Marey,  Vivenot,  and  Duchek 


Fig  58.  —  Sphygmograplilcal  tracing  of  the  normal  pulse. 

have  rendered  the  mechanism  of  this  phenomenon  plain.  It 
was  at  first  attributed  to  a  returning  wave,  produced  either 
by  the  closure  of  the  sigmoid  valves  or  by  the  reflux  of  a 
pulsation,  which  is  reflected  by  the  sharp  division  fold  at 
the  bifurcation  of  the  aorta  into  the  two  iliacs.  Every  fact 
now  seems  to  prove  that  the  dicrotism  is  owing  to  the  elas- 
ticity of  the  artery,  which,  having  been  distended  by  the 
ventricular  systole,  returns  to  its  former  size.  The  shght 
ascension,  interrupting  the  line  of  descent  (Fig.  53,  d),  marks 
the  exact  moment  when,  as  we  said  before,  the  arterial  elas- 
ticity restores  to  the  blood  wave  the  force  which  it  had  stored 
up,  and  which  would  be  lost  in  a  rigid  tube,  being  expended 
in  friction  (see  p.  155,  above).^  By  means  of  the  sphygmo- 
graph many  other  peculiarities  of  the  circulation  have  been 
observed :  for  instance,  in  deep  inspirations  the  negative 
waves  increase  in  depth,  while  they  diminish  when  forcible 
expiration  accompanies  the  strong  pressure  which  takes  place 

'  See  Lorain,   "  Etudes   de  Medecine  Clinique;"     Du   Pouls, 
1870,  in  8vo. 


158 


THE  BLOOD  AND  ITS  CIRCULATION. 


in  the  thorax :  the  positive  waves  then  increase  (see  Respira- 
tion). It  has  been  thought  that  under  certain  circumstances 
the  right  pulse  is  more  or  less  rapid  than  the  left :  this  is 
what  is  called  the  differing  pulse.  This  supposition  arose 
from  errors  in  observation.  The  difference  is  simply  due 
to   accidental   rhythmical   contractions  of  satellite   muscles 

of  the  arteries,  the  cora- 
co-brachial,  for  instance, 
in  the  case  of  the  radial 
pulse. 

Besides  these  elastic 
properties,  belonging  to 
the  muscle  and  to  the 
yellow  tissue,  by  means 
of  which  the  arteries 
regulate  the  general  cir- 
culation, these  vessels 
have  also  power,  by  the 
contraction  of  their 
smooth  muscles,  to 
change  their  size  con- 
siderably, and  in  this 
way  influence  the  circu- 
lation. As  these  mus- 
cles abound  in  the  small 
vessels  (see  Fig.  50),  it 
is  principally  the  local 
circulations  which  are 
thus  modified,  these 
variations  in  diameter 
being  scarcely  observ- 
able in  the  large  arte- 
ries. In  general,  the 
small  arteries  contract 
more  or  less,  according  as 
they  may  be  more  or  less 
well  nourished.  These 
contractile  properties 
are  made  use  of  in  sur- 
gery, and  the  hemostat- 
ics employed  are  useful, 
not  only  because  they  coagulate  the  blood,  but  also  because 

*  Irregular  contractions  of  the  small  vessels  of  the  interdi.c^ital  membrane  of 
a  frog.    The  contraction  is  produced  by  irritation.    (Wharton  Jones.) 


Big.  54.  — Contraction  of  the  small  arteries.* 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.    15^0 

they  excite  the  contraction  of  the  small  arteries,  and  thus 
diminish  their  size :  cold,  especially,  serves  to  produce  con- 
traction, as  may  be  verified  in  the  mesentery  of  a  frog 
(experiment  by  Schwann)  ;  in  this  case  the  small  arteries 
diminish  to  one-seventh  of  their  calibre  (Fig.  54).  In  the 
normal  state  the  arterial  muscle  is  sometimes  contracted,  and 
sometimes  relaxed ;  but,  taking  into  account  the  vaiiations  in 
size,  and  the  changes  in  the  circulation  resulting  froui  them, 
we  can  in  this  only  see  rhythmical  contractions  calculated  to 
assist  those  of  the  heart.  The  arterial  muscle  takes  no  active 
part  in  the  pulsation :  in  this  phenomenon  it  is  simply  pas- 
sive, as  we  have  already  shown. 

Capillaries.  —  The  diameter  of  these  vessels  is  extremely 
small :  in  the  smallest  it  is  hardly  sufficient  to  allow  of  the 
passage  of  a  blood  globule;  the  size,  however,  differs  in 
different  parts.  The  capillaries  of  the  skin  are  large  in  com- 
parison with  those  of  the  lungs  or  of  the  brain,  and,  on 
account  of  the  size  of  the  capillaries  of  the  fingers,  it  is  easy 
to  inject  through  the  arteries  the  commencement  of  the  veins 
of  the  foot  or  of  the  hand. 

The  capillaries  are  generally  formed  of  coats  of  very  simple 
structure :  their  tissue  is  apparently  amorphous,  but  traces  of 
cellular  structure  are  found  in  them,  in  the  shape  of  laminated 
flattened  plates,  the  remains  of  ancient  cells,  which  have  lost 
the  principal  physiological  properties  of  the  globular  element 
when  losing  its  form.  The  capillaries  haVe  not,  however, 
perhaps,  always  distinct  walls :  this  is  probably  the  case  with 
the  capillaries  of  the  liver,  which  are,  apparently,  only  lacunae 
hollowed  out  in  the  substance  of  tliis  organ  (interstices  be- 
tween groups  of  hepatic  cells). 

What  we  have  already  seen  shows  that,  in  general,  the 
circulation  is  continued  in  the  capillaries,  and  that  the  car- 
diac wave  is  felt  in  them  only  under  exceptional  circum- 
stances. We  have  also  studied  and  explained  the  presence 
of  what  is  called  the  inert  layer  (see  Fig.  43,  above). 

The  capillaries  are  not  contractile :  their  structure  forbids 
our  attributing  this  property  to  them,  and  all  the  phenom- 
ena of  dilatation  or  contraction  which  we  observe  in  them 
are  entirely  passive,  owing  to  similar  phenomena  taking 
place  in  the  small  arteries  and  veins.  The  ancient  physiolo- 
gists believed  with  Bichat  that  the  function  of  the  capillaries 
was  active,  and  that  they  are  very  contractile ;  they  considered 
them  as  forming  a  peripheral  heart.  Glisson's  capsule,  a 
fibrous  tissue  surrounding  the  vascular  network  of  the  liver, 


160  THE  BLOOD  AND  ITS   CIRCULATION. 

was,  according  to  them,  one  of  these  oTgans  of  peripheral 
impulse,  intended  to  aid  the  action  of  the  heart.  We  can 
easily  see,  by  our  study  of  the  circulation,  that  the  contrac- 
tion of  the  capillaries,  the  so-called  accessory  hearts^  would  be 
rather  an  obstacle  than  an  assistance  to  the  flow  of  the  blood. 
The  pulsations  felt  in  an  inflamed  tissue  (in  a  whitlow,  for 
instance)  were  adduced  as  a  proof  of  the  rhythmical  con- 
traction of  the  capillaries,  but  we  have  already  explained 
this  sensation  as  being  caused  by  a  paralytic  dilatation  of 
the  smaller  arteries.  We  have  also  seen  that  the  eff*ect  of 
hemostatic  agents  is  to  produce  the  contraction,  not  of  the 
capillaries,  but  of  the  small  arterial  vessels.  The  so-called  con- 
tractility of  the  capillaries  thus  belongs  entirely  to  the  region 
of  theory,  and  rests  on  no  positive  fact ;  and  the  experiments 
made  on  the  mesentery  of  a  fi-og  have  reference  to  contrac- 
tion of  the  small  arteries,  and  not  of  the  capillaries. 

The  capillaries,  as  we  have  considered  them,  form  a  per- 
fectly well-defined  part  of  the  circulating  system,  and  their 
physiological  properties  are  quite  distinct  from  those  of  the 
arteries  and  the  veins :  we  consider  as  capillaries^  with  Kol- 
liker  and  C.  Morel,  only  those  small  vessels,  which,  without 
undergoing  any  previous  preparation,  appear  as  tubes  of  an 
amorphous  substance  in  which  oval  nuclei  are  inserted. 
Some  histologists,  however,  Henle  and  Charles  Robin  in 
particular,  class  under  this  denomination  both  the  capillaries 
properly  so  called,  and  the  finest  ramifications  of  the  small 
arteries  and  veins.  Thus  Ch.  Robin  divides  the  capillaries 
into  three  kinds :  1,  capillaries  properly  so  called,  distin- 
guished by  having  a  single  homogeneous  tunic  with  a 
nucleus,  their  diameter  being  from  toW  ^^  ^  millimetre  (the 
diameter  of  a  blood  globule)  to  x§§(j  of  a  millimetre;  2, 
capillaries  of  the  second  kind,  having  a  diameter  of  from 
To  oiT  *^  ToOiT  ^^  ^  millimetre,  and  provided  with  a  double 
coat,  the  inner  one  being  a  continuation  of  the  outer,  which 
is  formed  of  contractile  cellular  fibres  arranged  in  circles ; 
8,  capillaries  of  the  third  kind,  their  diameter  being  from 
tVtf  ^o  tA%  ^"^  having,  beside  those  already  mentioned,  a 
third  external  tunic  formed  of  connective  tissue.  For  the 
physiologist,  these  two  latter  kinds  of  vessels  are  evidently 
small  arteries  and  veins,  likewise  possessing  great  contrac- 
tility ;  they  represent,  exactly,  the  base  of  the  arterial  and 
venous  cone,  which  abounds  in  smooth  muscular  elements, 
to  the  exclusion  of  the  elastic  element. 

The  structure  of  the  capillaries,  properly  so  called,  is  not. 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.    161 

however,  so  simple  as  an  examination  of  them,  without  the 
use  of  reagents,  would  lead  us  to  suppose  :  the  researches  of 
Auerbach,  Eberth,  and  Aeby,  and  the  method  of  impregna- 
tion by  nitrate  of  silver,  employed  by  Chrzonsczewsky,  have 
proved  that  the  capillaries  are  lined  with  a  pavement  epi- 
thelium (endothelium)  exactly  similar  to  that  which  forms 
the  inner  layer  of  the  arteries  and  the  veins:  outside  this 
endothelium  the  capillary  coat  is  formed  by  a  layer  of  cells, 
placed  close  together;  so  that  we  can  no  longer  consider  the 
capillaries  as  produced  by  the  end  to  end  fusion  of  cells,  whose 
cavity  would  thus  become  the  lumen  (or  interior  space),  and 
the  membranes  the  coat  of  the  capillary.  This  way  of 
regarding  the  development  of  the  capillaries  was  first  sug- 
gested by  Schwann  and  Kolliker,  as  the  result  of  their 
experiments  on  the  tail  of  young  toads,  and  appeared  to  con- 
firm the  experiments  of  Balbiani  on  the  cicatrization  of 
wounds  in  the  same  animals ;  this  theory,  however,  could 
not  stand  before  the  discovery  of  an  endothelium  in  the 
cavity  of  the  capillary ;  from  that  time,  this  cavity  has  no 
longer  been  looked  upon  as  an  intracellular^  but  as  an  inter- 
cellular^ space.  The  study  of  its  development  (His,  Afana- 
sieff,  Rouget)  proves  that  the  capillaries  not  only  possess  this 
endothelium,  but  that  it  is  enclosed  in  another  layer  of  cells : 
the  coat  of  the  capillaries,  when  in  course  of  development,  is 
composed  on  either  side  of  two  layers  of  cells  placed  end  to 
end,  in  such  a  manner  that  the  vascular  cavity  is  a  canal 
hollowed  out  between  these  double  layers  of  cells.^ 

1  The  structure  of  the  capillaries  and  the  small  vessels  (small 
arteries  and  veins)  does  not  as  yet  enable  us  to  explain  the  phe- 
nomenon of  diapedesis,  or  protrusion  of  the  globules,  which  some 
observers  have  witnessed,  and  which  many  pathologists  look  upon 
as  one  of  the  som-ces  of  suppuration.  We  have  seen  that  the 
white  globules  of  the  blood  and  the  globules  of  the  pus  are  exactly 
similar,  as  also  the  globules  of  the  lymph,  whence  the  theory  arose 
that  the  pus  globules  were  only  white  globules  of  the  blood  which  had 
left  the  vessels.  Cohuheim  (1869)  asserts  that,  iu  his  investigations 
on  inflammation  of  the  cornea  and  the  mesentery  of  the  frog,  this 
hypothesis  was  verified  by  experiment,  and  that  he  saw  the  diapedesis 
of  the  white  globules.  Hayem  has  made  the  same  observations,  and 
states,  moreover,  that  diapedesis  of  the  red  globules  also  takes  place, 
especially  under  the  influence  of  an  excess  of  pressure  produced  by 
ligature  of  the  veins.  This  question  of  pathological  physiology  is 
too  important  to  be  passed  over  here,  but  it  is  at  the  same  time  one 
on  which  there  is  so  much  diiference  of  opinion  that  we  can  only 
mention  it.     The  theory  of  diapedesis  has  many  partisans  in  the 

11 


162  THE  BLOOD  AND  ITS  CIRCULATION. 

These  rapidly  sketched  histological  details  show  that  our 
present  ideas  might  easily  change  on  the  subject  of  the  prop- 
erties of  the  globules,  especially  their  contractility:  their 
coats  are  composed  of  globules  which  have,  no  doubt,  pre- 
served the  properties  of  the  living  globule  :  Strieker,  indeed, 
has  no  hesitation  in  pronouncing  these  coats  contractile ;  he 
asserts  that  he  has  demonstrated  that  the  capillary  coats  of 
toads  possess  a  contractility  shown  by  alternate  shrinking 
and  enlargement,  and  thus  believes  himself  authorized  in 
attributing  the  same  property  to  the  capillaries  of  completely 
developed  animals.  If  this  view  is  confirmed,  it  will  not  be 
so  necessary  in  future,  in  a  physiological  point  of  view,  to 
distinguish  the  capillaries  properly  so  called,  from  the  small 
arteries  and  veins,  and  we  may  allow  that  there  are  several 
varieties  of  capillaries.     (See  p.  160.) 

We  will  add,  finally,  that  the  investigations  of  Sucquet 
and  Pean  show  that  the  communication  between  the  arterial 
and  the  venous  cone  is  sometimes  made  without  the  medium 
of  the  capillaries,  by  means  of  small  intermediate  vessels, 
visible  to  the  naked  eye,  and  abounding  in  muscular  ele- 
ments :  it  is  asserted  that  these  vessels  sometimes  contract, 
but  under  other  circumstances  dilate,  leaving  an  easy  pas- 
sage to  the  arterial  blood,  which  flows  directly  into  the 
veins,  the  capillary  circulation  being  reduced  to  its  minimum, 
whence  the  name  of  derivative  circulation.  This  disposition, 
which  all  anatomists  have  refused  to  admit  until  now  (it  is 
denied  by  Vulpian)  is  found,  according  to  Sucquet,  especially 
in  the  extremity  of  the  fingers  and  toes,  in  the  front  of  the 
knee  and  the  back  of  the  elbow,  in  the  skin  of  the  lips,  the 
cheeks,  the  nose,  the  eyelids,  the  mucous  membrane  of 
the  nasal  chambers  and  of  the  tongue. 

French  schools:  though  rejected  by  Ch.  Robin,  it  is-  held  without 
any  restriction  by  Vulpian  and  Charcot,  who  make  it  the  basis  of 
their  teaching  on  the  subject  of  inflammation.  We  must  add  that, 
in  a  course  of  experiments  made  personally,  we  have  remarked  the 
passage  of  the  white  globules  only  under  exceptional  circumstances, 
and  when  suppuration,  which  was  already  far  advanced,  had  brought 
the  vascular  coats  back  into  the  embryo  state.  (See  Duval  and 
Strauss,  "  Archiv.  de  Physiol.,"  1872.)  Messrs.  Feltz  and  Picot 
have  also  published  observations  opposed  to  the  theory  of  diapedesis 
("  Journal  de  1' Anatomic  "  of  Ch.  Robin,  1871-1878). 

See  also  a  late  monograph  by  Cohnheim,  wherein  he  asserts  the 
true  nature  of  inflammation  is  not  yet  discovered,  the  passage  of 
the  globule  being  attributed  to  a  secondary  rather  than  a  primary 
cause  of  the  pain,  heat,  and  redness. 


PERIPHERIC  ORGANS  OF  THE   CIRCULATION.    163 

Veins.  —  The  structure  of  the  veins  closely  resembles  that 
of  the  arteries ;  they  are,  however,  distinguished  from  them 
by  containing  much  less  elastic  tissue,  and  thus  have  no 
tendency  to  remain  open,  even  in  the  dead  body,  after  the 
blood  has  run  out. 

These  vessels  are,  nevertheless,  very  contractile,. but  the 
muscular  element  in  them  is  unequally  distributed.  Their 
contractions  may  be  easily  observed ;  for  instance,  we  see  the 
veins  of  the  hand  contract  and  shrink  when  immersed  in  cold 
water;  a  sudden  blow,  or  slight  percussion  of  a  subcutaneous 
vein,  produces  immediate  contraction,  followed  shortly  by 
paralysis  which  causes  the  vessel  to  dilate ;  and  we  sometimes 
see  these  two  phenomena  succeed  each  other  irregularly. 
These  contractions  of  the  veins  assist  the  circulation,  but 
their  rhythm  is  never  regularly  intermittent ;  there  is  really 
no  systole  or  diastole,  properly  so  called.  The  effect  of  the 
contraction  is  to  diminish  the  size  of  the  vessel,  and  to  drive 
the  blood  always  in  the  same  direction,  on  account  of  the 
valves,  of  which  we  shall  speak  presently. 

The  veins  are  very  dilatable,  owing  to  the  elasticity  of  the 
muscular  elements  which  compose  their  coats,  and  we  may 
say  that  one  of  their  principal  functions  is  to  promote  the 
easy  flow  of  blood  from  the  capillaries.  Thus  we  see  that 
the  veins,  beside  taking  the  part  of  conduits,  also  serve  as  a 
reservoir,  especially  at  the  summit  of  the  venous  cone,  in 
the  auricle.  For  this  purpose,  the  veins  are  sometimes 
developed  in  the  form  of  plexus,  and  this  arrangement  in- 
creases their  capacity  as  a  whole ;  these  plexus  may  also  be 
sometimes  intended  to  warm  the  parts  in  which  they  are 
situated,  as  we  shall  see  is  the  case  with  the  choroid  plexus 
(heating  apparatus  of  the  retina)  ;  but  their  object  is  gener- 
ally to  prevent  stagnation  in  the  capillaries,  and  they  are 
therefore  arranged  and  grouped  in  parts  where  they  will  not 
be  subject  to  compression,  as,  for  instance,  behind  the  body 
of  the  vertebrae  (between  this  body  and  the  posterior  com- 
mon ligament.)  Moreover,  the  ramified  form  and  the  anas- 
tomoses of  these  plexus  prevent  any  partial  and  local  com- 
pression from  impeding  the  return  of  the  circulation,  the 
blood  finding  always  an  easy  passage  through  the  vessels 
which  have  remained  open.  Finally,  there  are  some  veins 
whose  coats  are  inextensible  and  incompressible,  so  that 
nothing  can  hinder  the  circulation  in  them ;  and,  on  the  other 
hand,  they  cannot  swell,  so   as  to  compress  the   adjacent 


164  THE  BLOOD  AND  ITS   CIRCULATION. 

organs :  the  veins  of  the  dura  mater  offer  the  best  example 
of  this  arrangement. 

The  veins  are  generally  furnished  with  valves^  arranged  in 
such  a  manner  that  when  any  abnormal  pressure  takes  place, 
they  straighten  under  the  influence  of  the  current  of  blood, 
which  has  a  tendency  to  flow  back,  obliterate  the  lumen  of 
the  vessel,  and  prevent  the  blood  from  returning  to  the 
capillaries.  These  valves  thus  serve  to  neutralize,  an  1  even 
to  utilize  in  regard  to  the  circulation,  the  action  of  the 
shock,  and  of  accidental  pressure  (for  instance,  on  the  part 
of  the  neighboring  muscles,  when  contracted) ;  they  also 
serve  to  support,  by  their  division,  the  long  blood  columns, 
as,  for  example,  the  venous  column  of  the  lower  limbs.  The 
veins  supporting  long  columns  of  this  kind  have  remarkably 
thick  coats ;  thus  the  coats  of  the  saphenous  veins  resemble 
in  appearance  those  of  the  arteries,  and  remain  open  after 
incision,  in  the  same  manner  as  the  large  arterial  vessels. 
Where  local  pressure  is  rare,  no  valves  are  found  in  the 
veins,  as  in  the  venous  apparatus  of  the  brain  and  lungs. 

As  the  phenomena  of  the  flow  outwards  and  backwards  of 
the  blood  through  the  cardiac  orifices  gives  rise  to  particular 
sounds  (sounds  of  the  heart,  page  140),  so  the  peripheral 
circulation  occasions  sonorous  phenomena,  which  may  be 
better  observed  in  pathological  cases  (anaemia)  than  in  the 
normal  condition,  and  are  heard  especially  about  the  neck,  no 
doubt  because  the  aponeuroses  of  this  region,  by  their  special 
arrangement,  cause  a  state  of  tension  in  the  coats  of  the  vessels 
and  in  their  sheath,  which  is  favorable  to  the  transmission  of 
sounds:  the  tone  of  these  sounds  differs  very  much  (whistling 
sound,  musical  sound,  bruit  de  diable)  ;  they  are  sometimes 
continuous,  and  sometimes  intermittent;  some  are  produced 
in  the  arteries,  and  others  in  the  veins.  Weber  supposes 
them  to  be  caused  by  the  coats  of  the  vessels  being  made  to 
vibrate  by  the  motion  of  the  blood,  —  but  these  sounds  are 
more  generally  attributed,  as  is  done  by  Chauveau  and 
Potain,  to  the  blood  passing  rapidly  through  a  narrow  and 
then  through  a  wider  passage,  through  which  it  flows  moi-e 
slowly.  Chauveau  has  shown,  indeed,  that  vibrations  are 
produced  under  these  circumstances,  by  means  of  a  fluid 
vein,  which  causes  a  sort  of  eddy  at  the  point  where  the 
narrow  part  joins  the  wider  {fluid  veins  of  Savart).  This 
arrangement  may  be  carried  out  in  different  ways;  normally, 
as  at  the  opening  of  the  jugular  vein  into  the  subclavian ; 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.  165 

accidentally,  as  by  the  compression  of  the  vessel  by  a  mus- 
cle, by  the  stretching  of  an  aponeurosis,  and,  most  frequently, 
simply  by  the  application  of  the  stethoscope.  By  reproduc- 
ing these  sounds,  in  glass  tubes,  Heynsius  (of  Utrecht)  has 
made  the  movements  of  the  fluid  visible,  by  means  of  colored 
particles  in  suspension  following  the  eddying  and  whirling, 
which  become  more  rapid  as  the  sound  is  more  decided. 

It  has  been  also  ascertained  by  these  experiments,  that 
fluids  of  slight  density  produce  sounds  more  readily  than  the 
denser  fluids.  This  fact  explains  the  existence  and  intensity 
of  the  vascular  sounds  in  anaemia  and  chlorosis ;  in  these 
cases  the  quantity  of  blood  globules  is  diminished,  often  in 
such  proportion  as  to  lower  considerably  the  density  of  the 
blood  ;  we  need  not,  with  Peter,  look  for  a  spasm  of  the 
arterial  muscles  and  the  contraction  of  the  vessel,  to  produce 
the  phenomenon  of  the  fluid  vein.  Andral's  researches  have 
shown  that  there  is  always  a  vascular  souffle  when  the  num- 
ber of  globules  descends  below  the  proportion  of  80  to  1000 
(eight  per  cent),  and  that  its  intensity  depends  on  the  degree 
of  diminution  of  the  globules. 

III.   Influence  of  the  Nervous  System  on  the  Circu- 
lation. 

We  have  ascertained  the  existence  of  many  musculai 
phenomena  in  the  heart  and  in  the  vessels  (arteries  and 
veins) ;  this  makes  it  probable  that  the  contraction  of  these 
muscles  is  influenced  by  the  nervous  system. 

The  Heart  — It  was  however  long  believed  (as  by  Ilaller), 
that  the  heart  is  independent  of  the  nervous  system,  and 
that  the  afflux  of  blood  causes  the  contraction  of  this,  hollow 
muscle,  its  presence  directly  exciting  the  muscular  fibre  of 
the  cardiac  coats.  Now,  it  has  been  proved  beyond  dispute, 
that  the  movements  of  the  heart  as  well  as  the  other  move- 
ments are  governed  by  the  nervous  system.  The  spinal 
cord  appears  to  be  the  centre  of  this  influence,  and  we  know 
that  any  cerebro-spinal  shock,  or  injury  to  the  spinal  axis 
may  slacken  or  accelerate  the  motion  of  the  heart ;  this 
influence  may  be  reflex,  and  a  large  number  of  peripheral 
impressions  may  thus  hasten  or  slacken  the  movement. 
This  is  because  the  spinal  cord  and  the  bulb  furnish  nerves  to 
the  heart,  the  eff*ect  of  some  of  which  (branches  of  the  great 
sympathetic)  is  to  quicken  its  pulsations,  while  that  of  othei'S 
(the  pneumo-gastric)  is  to  retard  these :    thus  the  pneumo- 


166  THE  BLOOD  AND  ITS   CIRCULATION. 

gastric  \%  ^  paralyzing  nerve  of  the  heart  (Weber  and  Budge). 
We  shall  observe  similar  facts  in  the  innervation  of  the 
vessels. 

Moderating  Nerves  of  the  Heart.  —  Budge,  Weber,  and 
CI.  Bernard  (1848)  discovered,  almost  at  the  same  time, 
that  excitation  of  the  entire  pneumo-gastric  nerve,  or  of  its 
peripheral  extremity  only,  has  the  effect  of  retarding  the 
motion  of  the  heart ;  thus  in  the  dog,  an  animal  whose  heart 
beats  irregularly  and  very  rapidly,  such  excitation  serves  to 
regulate  the  cardiac  pulsation.  Different  explanations  have 
been  given  of  this  phenomenon ;  some  have  considered  that 
retardation  of  the  motion  of  the  heart  is  caused  by  exhaustion 
succeeding  too  violent  excitation  of  the  pneumo-gastric  neiTC : 
a  nerve  leading  to  a  muscle  could  be  looked  upon  only  as  an 
exciting  agent  of  this  muscle,  and  the  exhaustion  of  the  nerve 
seemed  to  explain  the  retardation  which  follows  excitation. 
This  explanation,  however,  does  not  apply  to  the  retardation 
which  follows  excitation  of  the  peripheral  extremity  of  a 
nerve  which  has  been  previously  cut ;  and  it  fails  especially 
when  we  consider  that,  by  simply  cutting  the  pneumo-gastric 
nerve,  the  rapidity  of  the  pulsations  of  the  heart  is  greatly 
increased.  Since  observation  of  similar  phenomena  in  other 
parts  of  the  nervous  system,  has  lately  made  the  idea  familiar 
to  us  of  nerves  possessing  paralyzing  properties,  it  is  gener- 
ally admitted  that  the  pneumo-gastric  nerve  is  a  moderating 
nerve  of  the  heart :  section  of  this  nerve  suppresses  the  mod- 
erating influence,  and,  consequently  renders  the  pulsation 
more  rapid ;  excitation  increases  the  moderating  influence, 
and  thus  retards  the  pulsation.  The  theories  by  which  it 
has  been  sought  to  explain  the  foregoing  experiment,  while 
denying  the  moderating,  paralyzing  function  of  the  pneumo- 
gastric  nerve,  are  in  many  cases  extremely  complicated,  and 
we  will  only  mention  here  the  facts  most  recently  furnished 
by  experiment.  Legros  and  Onimus,  who  examined  the 
effects  produced  by  excitation  of  the  pneumo-gastric  nerve 
by  intermittent  currents  of  electricity,  have  shown  that, 
under  these  conditions,  the  pulsations  become  fuller  and  less 
frequent  in  exact  proportion  to  the  number  of  intermissions; 
the  number  of  intermissions  required  to  produce  stoppage  of 
the  heart  is  smaller  when  the  animal  is  weakened  or  chilled, 
or  in  a  state  of  hibernation.  Arloing  and  Tripier  have  re- 
marked that  excitation  of*  the  right  pneumo-gastric  nerve 
has  more  effect  on  the  action  of  the  heart  than  that  of  the 
left.     (It  should  be  added  that  study  of  the  comparative 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.         167 

influence  of  these  two  nerves  on  respiration  has  induced 
tliese  authors  to  allow  that  the  left  pneumo-gastric  nerve 
acts  especially  on  the  lung.) 

Recent  investigations  by  Schiff*,  however,  appear  to  show* 
that  some  of  the  nerV^ous  fibres  which  accelerate  the  pulsation 
of  the  heart,  are  contained,  at  least  in  the  dog,  in  the  pneumo 
gastric  nerve  (Schiff,  Lo  Sperimentale^  Novembre,  1872.) 
These  fibres  appear  to  come  from  the  accessory  nerve  of 
Willis  (N.  Spinalis),  and  to  join  the  pneumo-gastric  nerve 
for  an  instant,  quitting  it  with  the  superior  laryngeal  nerve, 
and  reaching  the  heart  after  following  a  most  remarkable 
course,  not  unlike  Galen's  anastomosis:  (tliis  anastomosis 
unites  the  superior  laryngeal  nerve  to  the  inferior,  which  also 
furnishes  a  cardiac  nerve  of  its  own). 

Accelerating  Nerves  of  the  Heart.  —  The  influence  which 
the  cord,  by  means  of  the  great  sympathetic  nerve,  exercises 
on  the  heart,  in  increasing  both  the  force  and  number  of  its 
pulsations,  has  been  variously  explained,  and  the  investiga- 
tions made  on  this  subject  have  resulted  in  the  discovery  of 
a  nerve  whose  functions  are  very  peculiar.  This  is  the  nerve 
of  Cyon,  a  sensory  nerve  of  the  heart;  and  by  means  of  this 
the  heart  produces  a  reflex  action  which  causes  the  organs 
of  the  peripheral  circulation  to  dilate,  and,  consequently, 
enables  the  heart  to  diminish  the  energy  and  number  of  its 
efforts.  We  borrow  from  CI.  Bernard's  recent  lectures  (May, 
1872),  and  from  his  report  to  the  Academy  of  Sciences  on 
Cyon's  experiments,  our  account  of  this  interesting  question. 

Le  Gallois  first  pointed  out  the  influence  of  the  spinal  cord 
on  the  pulsation  of  the  heart.  But  Von  Bezold,  by  his  ex- 
periments, in  1863,  proved  more  pailicularly  that  section  of 
the  cord  between  the  occipital  region  and  the  atlas,  produces 
considerable  diminution  of  the  pressure  of  the  blood  in  the 
large  arteries,  as  well  as  retardation  in  the  pulsations  of  the 
heart.  He  afterwards  proved  that  excitation  of  the  cord 
behind  this  section  restores  both  the  pressure  of  the  blood, 
and  the  rapidity  of  the  pulsation,  thus  showing  that  the 
effect  of  the  cord  upon  the  heart  is  to  modify  the  force  and 
number  of  pulsations. 

Ludwig  and  Thiry,  however,  having  observed  that  excita- 
tion of  the  cord,  separated  from  the  brain,  always  exerts  its 
influence  on  the  pressure  of  the  blood,  even  when  the  cardiac 
nerves  which  unite  the  heart  to  the  cord  have  been  de- 
stroyed, inferred  from  this  that  the  cord  has  no  real  influ- 
ence upon  the  heart  itself^  but  upon  the  periphei*al  circulating 


168  THE  BLOOD  AND  ITS  CIRCULATION, 

system;  and  Ludwig  and  Cyon  proved,  by  new  experiments, 
that  this  influence  on  the  peri[)heral  circulating  system  is 
principally  exercised  in  vascularizing  the  abdominal  viscera, 
and  is  conveyed  to  them  by  the  medium  of  the  splanchnic 
nerves :  by  dividing  these  nerves  we  obtain  effects  similar  to 
those  which  result  from  section  of  the  cord  between  the  oc- 
ci])ital  bone  and  the  atlas. 

The  influence  of  the  cord  on  the  pressure  of  the  blood  (we 
are  not  now  speaking  of  the  number  of  pulsations)  is  as 
staled  by  Ludwig;  but  Cyon  has  also  demonstrated  that  this 
influence  which  is  the  result  of  a  peripheral  vaso-motor 
modification  (see  further  on,  vaso-motors),  is  by  nature 
reflex,  and  may  therefore  be  caused  by  excitation  of  a  sen- 
sory nerve,  beginning  in  the  heart  itself:  if,  after  cutting 
off  this  nerve,  which  is  a  branch  of  the  pneumo-gastric,  its 
peripheral  end  be  excited,  no  effect  is  produced  ;  but  excita- 
tion of  the  central  end  is  painful,  and  causes,  when  the 
manometer  is  applied  to  the  carotid  artery,  considerable 
diminution  of  pressure  from  a  reflex  influence  bearing  espe- 
cially on  the  abdominal  vascular  system  (splanchnic  nerves), 
resulting  in  paralysis  and  dilatation :  in  short,  the  depressing 
nerve  of  the  circulation  (of  Cyon),  represents  the  centripetal 
course  of  2i  paralyzing  reflex  action,  producing  depletion  of 
tlie  heart,  and,  consequently,  diminution  in  the  pressure  of 
the  blood  in  general. 

Under  the  influence  of  these  reflex  actions,  which  may 
also  have  their  starting  point  in  the  brain  (emotional  influ- 
ences, palpitations,  syncope,  owing  to  mental  causes),  the 
pulsations  of  the  heart  offer  the  greatest  possible  variety  in 
number  and  rhythm,  especially  in  cases  of  disease.  In  the 
normal  condition,  the  average  number  of  pulsations  is  72  a 
minute.  This  is  the  average  in  the  adult  stage,  its  minimum 
being  found  at  the  period  when  growth  ceases,  and  the  epi- 
physes are  found  united ;  statistics  seem  to  show  that  the 
heart  in  old  age  beats  faster  on  the  average  than  in  the  adult. 

In  the  pathological  condition,  the  changes  in  the  pulsation 
of  the  heart,  ascertained  by  the  throbbing  of  the  pulse,  sup- 
ply us  with  valuable  information  on  the  subject  of  the 
innervation  of  this  organ,  but  the  quickness  of  the  pulse 
yields  no  indication  as  to  the  state  of  the  circulation,  prop- 
erly so  called.  If  we  go  back  to  our  study  of  the  mechanism 
of  this  phenomenon,  we  shall  understand  how  the  pulse  may 
be  quick  without  the  circulation  being  active ;  if,  for  instance, 
the  heart  at  each  contraction  sends  out  less  than  the  usual 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.        169 

quantity  of  blood.  So,  at  the  moment  of  death,  the  pulse 
may  be  very  rapid,  while  the  circulation  declines. 

The  heart,  when  taken  from  the  body,  may  still  continue 
to  beat :  this  may  be  readily  observed  in  the  cold-blooded 
animals,  and  has  also  been  found  to  be  the  case  in  man  ;  we 
have  found  rhythmical  contractions  still  existing  in  the  heart 
of  an  executed  criminal  an  hour  after  death.  This  is,  how- 
ever, only  another  reflex  phenomenon,  the  centre  for  which  is 
found  in  small  ganglions  disseminated  throughout  the  sub- 
stance of  the  coats  of  the  heart,  principally  in  the  auricles 
and  the  auriculo-VQntricular  zones,  or,  at  all  events,  near  the 
base  of  the  heart.  If  the  heart  of  a  frog  be  cut  in  fragments, 
we  find  that  only  those  parts  of  the  ventricle  or  of  the  auri- 
cles which  adhere  to  the  base  continue  to  palpitate. 

The  position  of  these  ganglions,  or  small  reflex  centres, 
found  in  the  heart  itself,  has  been  ascertained  up  to  a  certain 
point:  there  are  three  principal  ones,  —  ganglion  of  Hemak, 
at  the  opening  of  the  lower  vena  cava;  ganglion  of  bidder, 
situated  in  the  left  auriculo-ventricular  septum ;  and  gan^ 
glion  of  Ludwig,  in  the  inter-auricular  septum. 

These  three  ganglions  do  not  all  appear  to  have  the  same 
function  :  the  two  former  appear  to  be  centres  of  excita- 
tion, and  the  latter  of  moderation.  If  the  heart  be  cut  into 
two  unequal  parts,  one  containing  Remak's  ganglion,  and 
the  other  those  of  Bidder  and  Ludwig,  the  first  will  continue 
to  palpitate,  while  the  other  remains  quiet.  If  then  the  auri- 
cles in  this  latter  part  be  separated  from  the  ventricle,  they 
will  remain  in  repose,  while  the  ventricle  again  begins  to 
throb.  Thus  we  see  that  each  of  the  outer  ganglions 
(Remak's  and  Bidder's)  cause  movements  which  the  inner 
ganglion  (Ludwig's)  paralyzes,  when  taken  in  connection 
with  only  one  of  the  two  first;  but  when  the  heart  is  entire, 
Jjudwig's  ganglion  is  unable  to  counterbalance  the  amount 
of  motor-power  of  the  other  two. 

The  starting-point  for  these  reflex  actions  is  the  excitation 
produced  by  the  presence  of  the  blood  on  the  sensory  (or 
centripetal)  fibres  in  the  endocardium,  and  not  directly  on 
the  muscular  fibre  itself.  A  substitute  for  this  physiological 
excitant  may  be  found,  in  experiments,  by  excitations  di- 
rected to  any  point  of  the  heart,  particularly  the  endocar- 
dium. If  the  contact  of  the  blood  with  the  endocardium  be 
prevented  the  heart  ceases  its  pulsations,  the  physiological 
cause  of  the  reflex  action  being  thus  removed.  If,  for  in- 
stance, the  chest,  and  consequently,  the  heart,  be  forcibly 


170  THE  BLOOD  AND  ITS  CIRCULATION. 

compressed  by  a  strong  expiration,  so  as  to  empty  it  com- 
pletely, and  bring  its  coats  into  close  contact,  we  may 
succeed  in  stopping  the  beating  of  the  heart.  This  explains 
those  curious  instances  of  persons  who  are  able  at  will,  to 
stop  the  motion,  and  consequently,  the  pulsation  of  their 
heart.     (See  respiration.) 

Vessels.  —  The  vessels  which  we  know  contract  under 
direct  excitation  (heat,  cold,  shock,  etc.),  are  also,  in  this 
respect  under  the  control  of  the  nervous  system.  CI.  Ber- 
nard has  demonstrated  that  effects  of  this  kind  belong 
especially  to  the  province  of  the  great  sympathetic  (vaso- 
motor nerve),  which  sometimes  produces  contraction  and 
sometimes  paralysis  of  the  muscular  coats  of  the  vessels. 
Some  of  the  cerebro-spinal  nerves  produce  the  same  effect. 
Thus  the  chorda  tympani  paralyzes  the  arteries  of  the 
sub-maxillary  gland.  These  phenomena  of  contraction 
or  dilatation  of  the  vessels  have  great  influence  on  the 
calorification  of  the  organs  in  which  they  take  place ;  they 
are  for  the  most  part  of  a  reflex  nature,  and  are  the  conse- 
quence either  of  an  impression  made  upon  sensory  nerves, 
or  of  some  mental  excitement  (redness  or  paleness  of  the 
face  under  the  influence  of  the  passions).  The  innervation 
of  the  vessels  thus  offers  the  closest  resemblance  to  that  of 
the  heart. 

The  physiology  of  the  great  sympathetic  as  a  vaso-raotor 
nerve  offers  great  difliculties,  not  only  in  this  general  point  of 
view,  but  also  in  that  of  its  influence  on  the  vessels,  the  origin 
of  its  nerve  filaments,  and  of  their  course  and  relation  to  the 
nerves  concerned  in  the  "animal"  processes  or  functions  {vie  de 
relation) . 

After  Henle  had  discovered  smooth  muscular  elements  in 
the  coats  of  the  arteries.  Stilling  found  nerves  which  disap- 
pear in  these  coats,  and  gave  these  the  name  of  vaso-motor 
nerves,  seeking  to  complete  the  anatomical  fact  by  a  physio- 
logical hypothesis.  Physiological  researches  on  the  subject, 
however,  only  date  as  far  back  as  1851,  when  CI.  Bernard 
showed  that  section  of  the  great  sympathetic  nerve  in  the 
neck  of  a  rabbit  produces  considerable  increase  of  temper- 
ature in  the  ear  of  the  corresponding  side ;  though  at  first 
tempted  to  ascribe  this  phenomenon  merely  to  a  calorific 
and  direct  action  of  the  nerves,  he  soon  saw  that  the  heat  of 
the  ear  was  simply  due  to  a  dilatation  of  the  blood-vessel, 
and  to  a  greater  afllux  of  blood;  and  showed,  simultaneously 
with  Brown-Sequard,  that  by  galvanizing  the  cephalic  ex- 


INFLUENCE   OF  THE  NERVOUS  SYSTEM.        171 

tremity  of  the  cervical  sympathetic  nei-ve,  when  cut  off,  a 
constriction  of  the  auricular  vessels  occurs,  and  consequently, 
a  return  to  the  normal  temperature,  or  even,  from  anaemia,  a 
lower  temperature  may  follow.  ' 

Since  that  time,  the  function  (role)  of  the  great  sympa- 
thetic, as  a  vaso-motor  nerve,  has  been  clearly  demonstrated 
in  other  parts  of  the  body,  the  limbs,  and  the  abdominal 
viscera,  as  well  as  of  the  head.  Kussmaul  and  Tenner  con- 
firmed the  opinion  that  the  calorific  influence  is  entirely 
vaso-motor,  and  Van  der  Beke  Callenfels  (1856)  proved  that 
this  afliux  of  blood  in  any  part  of  the  periphery  which  is 
much  exposed  to  radiation  causes  considerable  loss  of  heat 
in  the  animal. 

Experimental  physiology  of  the  great  sympathetic  as  a 
vaso-motor  nerve,  may  now  be  pursued  by  studying  the 
effects  produced  by  its  section  and  excitation,  as  has  been 
done  by  Mons.  Legros  in  his  monograph :  1.  Section  of  a 
sympathetic  branch  is  instantly  followed  by  the  paralyzation 
of  the  smooth  muscles  innervated  by  this  branch,  especially 
the  muscles  of  the  vessels:  the  small  vessels  are  seen  to 
dilate,  and  the  capillary  network  to  fill,  on  account  of  the 
increased  afflux  of  blood.  Generally  it  may  be  easily  ob- 
served in  a  rabbit's  ear,  for  instance,  that  vessels  which  were 
hardly  visible  before  the  operation,  can  be  distinctly  seen 
after  it.  In  short,  passive  hyperaemia  takes  place.  2.  By 
bringing  an  induced  current  of  electricity  to  bear  upon  the 
peripheric  extremity  of  the  sympathetic  nerve,  after  section, 
quite  a  contrary  phenomenon  is  produced:  the  vascular 
muscles  contract,  the  vessels  shrink,  and  active  anaemia 
follows.  If  the  excitation  ceases,  a  marked  dilatation  suc- 
ceeds. The  capillaries  are  entirely  passive  during  all  these 
phenomena:  the  whole  process  takes  place  in  the  small  veins 
and  arteries.  The  essentially  passive  part  played  by  the 
capillaries,  during  the  alternations  of  contraction  and  relaxa- 
tion going  on  in  the  vessels,  is  best  understood  by  studying 
the  pressure  or  vascular  tension  which  accompanies  experi- 
ments on  the  vaso-motor  nerves.  If,  indeed,  the  capillaries 
dilated,  as  do  the  arteries,  after  section  of  the  sympathetic 
nerve,  the  flow  of  blood  would  be  increased,  but  the  resist- 
ance would  be  less,  and  the  pressure  lower.  On  the  other  hand, 
if  excitation  of  the  sympathetic  nerve  caused  the  capillaries 
to  contract  as  do  the  other  vessels,  the  resistance  would  in- 


1  Ch.  Legros,  "  Des  nerfs  vaso-moteurs.'*     Paris,  1873. 


172  7HE  BLOOD  AND  ITS  CIRCULATION. 

crease,  and  the  tension  of  the  blood  also.  Now,  what  takes 
place  is  precisely  the  contrary ;  CI.  Bernard  has  shown  by 
the  aid  of  the  differential  manometer,  that  the  tension  is 
increased  in  the  first  instance,  and  diminished  in  the  second 
(Legros). 

But  how  does  the  great  sympathetic  nerve  act?  How 
does  it  happen  that  (during  the  condition  of  inactivity) 
it  keeps  the  vascular  coats  in  a  continued  state  of  contrac- 
tion ?  How  is  it  that,  at  certain  moments,  by  means  of 
reflex  actions,  this  nerve  causes  nearly  similar  phenomena  to 
those  which  it  exhibits  when  cut ;  such  as  dilatation  of  the 
vessels,  and  greater  afflux  of  blood  in  certain  parts  of  the 
organism  (sudden  redness  of  the  face,  turgescence  of  the  erec- 
tile tissues,  hyperaemia,  more  abundant  seci'etion  of  the 
glands,  etc.)  ? 

In  replying  to  the  first  question  a  constant  state  of  excita^ 
tion  of  the  vaso-motor  nerves  is  generally  admitted  :  this 
being  due  to  a  continuous  reflex  action  originating  in  the 
sensitive  nerves  of  the  arteries  (Audiffrent)  in  other  sensi- 
tive parts;  thus  the  muscular  tonus  has  been  looked  upon 
as  a  reflex  influence :  according  to  Brondgeest,  the  tonus 
may  be  made  to  cease  instantly  by  section  of  the  sensory 
nerves  proceeding  from  any  part  which  may  be  in  a  tonic  con- 
dition. According  to  other  physiologists,  the  constant  excita- 
tion of  the  vaso-motor  centre  is  produced  by  the  presence  of 
carbonic  acid  in  the  blood.  If  animals  be  poisoned  by  means 
of  this  acid,  all  the  small  arteries  will  be  found  in  a  con- 
tracted state  (Thiry). 

The  second  question  is  still  more  difficult  to  answer.  It 
has  been  clearly  demonstrated  that  repeated  excitations  pro- 
duce dilatation  of  the  vessels  by  reflex  action  ;  if  the  ear 
of  a  rabbit  be  cut  off,  and  the  sciatic  nerve  excited,  we  see 
that  the  blood  flows  in  much  greater  abundance  through  the 
vessels  which  have  been  cut.  Again,  there  are  centrifugal 
nerves,  irritation  of  which  causes  instant  dilatation  of  the 
vessels;  thus  the  chorda  tympani,  if  irritated,  produces 
severe  hyperaemia,  and  consequently,  abundant  secretion  in 
the  sub-maxillary  gland. 

It  is  difficult  to  allow  the  existence  of  nerves  which  directly 
paralyze  the  muscular  elements  of  the  arterial  tunics;  for 
mstance,  the  chorda  tympani,  which  is  a  branch  of  the 
facial  nerve,  reminds  us  rather  of  those  nerves  which,  by 
their  influence  upon  others,  cause  all  action  to  cease  in  the 
latter,  by  a  sort  of  nervous  interference,  as  the  intervention 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.        173 

of  light  produces  darkness  by  joining  light  to  light.  Claude 
Bernard  appears  to  have  adopted  this  hypothesis,  and  it  miiy 
also  serve  to  explain  the  nervous  mechanism  of  the  afflux  of 
blood  in  erection :  the  nerves  coming  from  the  cord  act  upon 
the  threads  of  the  great  sympathetic  nerve  so  as  to  prevent 
their  action,  causing  turgescence  and  hyperaemia  of  the  erectile 
tissue.  Section  of  the  cord  does  not  cause  continuous  erec- 
tion, because  the  nervous  influx  of  the  spinal  (rachidian) 
nerves  can  no  longer  act  upon  the  sympathetic  nerves,  and 
this  association  of  nervous  influences  is  alone  capable  of  pro- 
ducing vaso-motor  paralysis.  In  adopting  this  hypothesis, 
the  influence  of  the  first  nerve  on  the  second  must  be  con- 
sidered as  equivalent  to  the  section  of  the  great  sympathetic 
nerve  made  by  an  operator  who  desires,  for  instance,  to  pro- 
duce hyperaemia  of  a  rabbit's  ear. 

This  view,  however,  does  not  satisfy  all  who  have  made 
the  experiment,  because  some  among  them  have  been  cou- 
vinced  that  more  serious  hyperaemia  takes  place  under  the 
influence  of  reflex  phenomena  in  a  less  degree  than  any 
which  may  be  caused  by  section  of  the  great  sympathetic 
nerve  in  the  same  parts :  the  idea  has  thus  been  suggested 
of  active  hypercemia^  more  intense  X\\2iii  passive  qv  paralytic 
hypercBTYiia^  and  two  theories  have  lately  been  formed  on  this 
subject;  tliat  of  Schiff*,  or  active  dilatation  of  the  vessels ^ 
that  of  Legros  and  Onimus,  or  peristaltism  of  the  vessels. 

This  theory  of  the  active  dilatation  of  the  vessels  was  for 
a  short  time  entertained  by  CI.  Bernard,  but  he  now  appears 
to  have  finally  renounced  it :  it  is  not  easy  to  prove  it  by 
anatomy,  for  it  supposes  the  existence  of  longitudinal  mus- 
cular fibres  in  the  coats  of  the  arteries,  and  of  these  histology 
shows  no  trace.  Schiflj  therefore,  carefully  abstains  ("  X,egons 
sur  la  Physiologic  de  la  Digestion  ")  from  stating  his  theory 
in  explicit  terms;  he  still  regards  as  inexplicable  both  the 
origin  and  the  mode  of  action  of  these  dilating  nerves,  but  he 
relates  many  experiments,  which,  to  his  view,  make  their  exist- 
ence undeniable. 

He  observed,  in  the  small  arteries  of  a  rabbit's  ear,  phe- 
nomena of  systole  and  diastole,  appearing  from  2  to  8  times 
in  a  minute  (this  by  no  means  coincides  with  the  beating  of 
the  heart).  These  movements  cannot  be  the  consequence 
of  alternate  contractions  of  the  veins,  for  direct  inspection  of 
these  vessels  reveals  nothing  of  the  kind ;  neither  are  they 
caused  by  paralysis  of  the  arteries  succeeding  to  a  momen- 


174  THE  BLOOD  AND  ITS   CIRCULATION. 

tary  contraction  for  the  diastole  observed  in  the  uninjured 
animal  is  ranch  greater  than  can  be  produced  by  section  of 
the  great  sympathetic  nerve,  in  other  words,  by  paralytic 
dilatation.  The  diastole  observed  would  be  then  really  an 
active  dilatation. 

Irritation  of  the  central  extremity  of  the  auriculo-cervical 
nerve  (auricular  branch  of  the  cervical  plexus)  produces,  by 
a  reflexive  course,  dilatation  of  the  vessels  of  the  ear;  this 
the  same  experiments  prove  to  be  an  essentially  active,  not 
paralytic  phenomenon  (there  is  no  contraction  of  the  veins, — 
paralytic  dilatation). 

Vaso-motor  reflexes  (reflex  actions)  of  a  similarly  active 
nature,  and  more  powerful  in  effect  than  the  paralyzing  in- 
fluences, have  been  observed  by  Schiff*,  by  placing  the  animal 
(dog  or  rabbit)  in  a  vapor-bath,  or  producing  in  it  a  septic 
fever,  exciting  its  passions,  etc. 

Finally,  Schiff*  ascertained  that  irritation  of  the  peripheral 
extremity  of  the  auricular  branch  of  the  trifacial  imme- 
diately produces  these  active  dilations ;  one  of  these  nerves, 
like  the  chorda  tympani,  acting  upon  these  organs  in  such  a 
manner  as  to  produce  in  X^iem.  functional  hypercemia^  which 
Schiff"  prefers  to  distinguish  from  neuro-paralytic  hyper oemia^ 
without,  however,  denying  the  existence  and  importance  of 
the  latter. 

The  theory  o?  t\\Q  peristaltism  of  the  arteries  is  more  com- 
plete; it  seeks  to  explain  normal  as  well  as  pathological 
facts,  and  enters  into  the  closest  details  of  the  question. 
Legros  and  Onimus  ground  this  theory  on  investigations  of 
three  kinds :  — 

1.  Direct  inspection  of  the  small  arteries  discloses  vermic- 
ular or  peristaltic  contractions,  beginning  in  the  principal 
trunks,  extending  to  the  smallest  arteries,  and  assisting  the 
progress  of  the  blood.  Goltz  and  Thiry  had  already  ascribed 
to  a  similar  mechanism  the  evacuation  of  the  arteries  after 
death.  Onimus  observed  these  movements  in  tlie  vessels  of 
the  inferior  animals  (annelida),  in  which  their  existence  had 
long  been  recognized,  but  he  has  besides  pointed  them  out  in 
the  interdigital  membrane  in  frogs,  and  even  in  man  in  the 
small  arteries  of  the  eye:  "if  the  central  artery  of  the  retina 
be  obstructed  by  a  clot,  we  see,  by  the  aid  of  the  ophthal- 
moscope, that  the  small  arteries,  which  show  the  existence 
of  a   collateral    circulation,   have   very   marked    peristaltic 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.        175 

2.  On  modifying  or  suppressing  the  action  of  the  heart, 
we  find  that  the  blood  still  circulates  in  the  arteries,  and 
flows  into  the  veins,  and,  under  these  circumstances,  an  injec- 
tion made  upon  a  dying  animal  is  most  likely  to  succeed,  the 
peristaltism  of  the  arteries  making  the  blood  penetrate  the 
finest  nets  of  the  capillaries.  The  weakening  of  the  heart  by 
the  administration  of  chloroform,  of  digitalis,  or  of  alcohol, 
in  an  animal  in  whom  the  cervical  portion  of  the  great  sym- 
pathetic is  cut  on  one  side,  produces  an  excess  of  tempera- 
ture, not  of  the  side  operated  upon,  but  of  the  other  side ; 
the  peristaltism  of  the  arteries  on  this  side  alone  bein_^  capa- 
ble of  producing  a  hypercemia,  which  may  be  called  active,  but 
must  not  be  confounded  with  the  active  dilatation  of  Schiff. 

3.  By  applying  irritants  to  the  peripheral  extremity  of  the 
sympathetic  nerve  when  cut,  we  produce  very  different  re- 
sults, according  as  the  excitations  produced  are  tetanic,  or 
calculated  to  bring  the  peristaltism  of  the  arterial  tunics  into 
play.  Thus,  while  powerful  excitants  produce  anaemia  of  a 
rabbit's  ear,  by  producing  a  state  of  energetic  and  permanent 
contraction,  we  find,  on  the  contrary,  that  a  slight  ligature, 
or  the  action  of  glycerine,  or  of  nitrate  of  silver,  etc.,  causes 
considerable  hypersemia,  more  important  even  than  passive 
hyperaemia  (neuro-paralytic) ;  these  results  are,  however, 
still  more  striking  if  electricity  be  employed.  While  inter- 
rupted currents  (faradaic)  paralyze  the  arteries  (causing 
anaemia),  we  find  that  the  continuous  current  (and  only 
when  its  direction  is  centrifugal)  produces  a  very  considerable 
hyperaemia  in  parts  to  which  the  sympathetic  nerve,  which  is 
thus  excited,  is  distributed.  Under  similar  circumstances, 
microscopical  examination  of  the  interdigital  membrane  of  a 
frog  reveals  very  decided  peristaltism  of  the  small  vessels, 
dui-ing  the  passage  of  the  centrifugal  continuous  current. 

Thus  certain  excitants  produce  in  the  arteries  slight  or 
clonic  contractions,  causing  peristaltism  and  subsequent 
hyperaemia.  Others  cause  tetanic  contractions,  bringing 
on  anaemia  and  chill. 

Differences  of  the  same  kind  are  observed  in  the  manner 
in  which  physiological  excitants,  the  passions,  for  instance, 
act  on  the  vascularity  of  the  skin  in  general,  and  on  that  of 
the  face  in  particular.  Moleschott,  who  was  attached  to  the 
theory  of  vaso-motor  paralyses,  had  already  divided  the  pas- 
sions into  paralyzing  and  exciting  passions ;  but  when  wo 
see,  for  instance,  a  slight  anger  cause  redness  of  the  face 
(red  anger)  and  a  greater  access  of  the  same  passion  produce 


176  THE  BLOOD  AND  ITS  CIRCULATION. 

paleness  (white  anger),  is  it  not  more  reasonable,  instead  of 
maintaining  that  a  low  degree  of  this  passion  is  paralyzing 
and  a  paroxysm  exciting,  to  see  in  the  first  case  a  slight, 
clonic  excitation,  causing  peristaltism  and  hyperaemia ;  and  in 
the  second  a  violent  tetanic  excitation,  producing  permanent 
constriction  of  the  vessels,  anasmia  and  extreme  paleness? 

We  see,  by  the  statement  of  these  different  and,  often, 
opposing  theories,  that  we  are  still  far  from  being  decided  as 
to  the  nature  of  the  vaso-motor  phenomena,  or  vascido- 
motors  (Beclard).  More  just  ideas,  up  to  a  certain  point,  have 
been  acquired  on  the  origin  and  course  of  the  vaso-motor 
nerve  fibres. 

The  vaso-motor  centres  are  placed,  partly  in  the  spinal 
cord,  but  principally  in  the  cephalic  (cerebral)  parts  of  the 
medullary  cord,  for  section  of  the  cervical  cord  causes  dilata- 
tion of  all  the  arteries  of  the  body.  Experiments  by  Ludwig, 
Thiry,  and  Schiff,  show  that  these  centres  are  placed  in 
the  protuberance  and  peduncles  of  the  brain :  here  take 
place  the  central  phenomena  of  reflexes  which,  after  irritation 
of  the  sensitive  nerves,  diminish  the  tonicity  of  the  vessels. 
Injury  to  the  cerebral  peduncles  causes  hyperiemia,  especially 
in  the  abdominal  viscera,  and  may  lead  to  softening  of  the 
gastric  mucous  membrane  or  coat  (Schiff).  Irritation  of 
these  peduncles  causes  retraction  of  all  the  vessels  (Budge). 
The  cerebellum  appears,  however,  to  have  some  share  in  the 
vaso-motor  operations,  and  the  cervical  cord  may  be  the  seat 
of  the  vaso-motor  phenomena  concerned  in  the  functions  of 
salivary  secretion. 

From  these  vaso-motor  centres  originate  centrifugal  fibres, 
following  the  spinal  axis,  and  passing  successively  to  the 
arteries  by  the  medium,  of  the  great  sympathetic  nerve. 
In  this  course  the  vaso-motor  nerves  follow  especially 
the  antero-lateral  columns :  they  cross  each  other,  for,  in 
hemiplegia  from  a  central  cause  the  vaso-motor  lesion,  as 
with  other  lesions  of  the  motor  tract,  is  observed  on  the 
opposite  side  to  that  of  the  encephalic  lesion ;  this  decus- 
sation, however,  as  with  the  voluntary  motor  nerves,  ap- 
pears to  be  made  suddenly  at  the  level  of  the  bulb,  and 
there  is  no  other  decussation  of  the  vaso-motor  nerves  in 
the  remainder  of  the  spinal  axis  (Brown-Sequard).  Thus, 
in  spinal  hemiplegia,  the  vaso-motor  disturbances  are  ob- 
served, like  those  of  the  motor  tract,  on  the  same  side  as 
the  medullary  disease,  and  on  the  opposite  side  to  the  dis- 
turbances  afiecting   sensation  (see  page   46)  :  that  is,  the 


INFLUENCE  OF  THE  NERVOUS  SYSTEM.        177 

paralyzed  member  is,  on  account  of  the  dilatation  of  its 
vessels,  warmer  than  the  sound  member;  but  continued 
motion,  and  consequently,  greater  intensity  of  combustion, 
in  the  latter,  may  cause  a  difference  of  temperature  in  the 
opposite  direction;  and  in  this  manner  must  be  explained 
those  contradictory  results  of  observations  which  have  sug- 
gested to  V.  Bezold  the  idea  that  the  vaso-motor  nerves 
of  the  inferior  extremities  remain  on  the  same  side  of  the 
spinal  cord,  while  those  of  the  anterior  extremity  are  inter- 
laced along  the  medullary  cord ;  while  Schiff  has  formed  the 
still ,  more  singular  hypothesis  that  the  course  of  the  vaso- 
motors of  the  leg,  the  foot,  the  hand,  and  the  forearm,  is 
direct;  whilst  those  of  the  pelvis,  the  thigh,  the  arm,  and  the 
shoulder,  are  crossed. 

The  vaso-motors  spring  from  the  cord  by  the  anterior  roots 
of  the  spinal  nerves.  This  fact  has  been  put  almost  beyond 
the  reach  of  doubt  by  Claude  Bernard's  investigations  of  the 
vaso-motors  of  the  thoracic  portion  of  those  which  control 
the  secretion  of  the  saliva,  and  finally,  of  those  sympathetic 
branches  which,  without  being  exactly  vaso-motors,  bear  the 
closest  relationship  to  these  nerves.  We  mean  those  fila- 
ments which  control  the  oculo-pupillary  phenomena,  which 
are  observed  to  take  place  nfter  section  of  the  cervical  sym- 
pathetic cord  (contraction  of  the  pupil,  sinking  of  the  eye- 
ball, etc.). 

What  is  remarkable,  though,  is  that  the  height  of  the  roots 
from  whijch  the  vaso-motors  sjjring  does  not  at  all  correspond 
to  the  height  of  the  organs  or  of  those  parts  in  which  these 
nerves  are  distributed  :  thus  CI.  Bernard  luis  demonstrated 
that  the  vaso-motors  which  join  the  brachial  plexus,  and 
then  proceed  to  the  thoracic  portion,  come  to  it  by  the 
ascending  filaments  of  the  thoracic  cord  of  the  great  sympa- 
thetic nerve,  those  which  join  the  sciatic  nerve  coming  by 
the  descending  filaments  of  the  lumbar  region  cord ;  they 
thus  emerge  from  the  spinal  cord  :  the  former  from  much 
lower,  and  the  latter  from  much  higher,  roots  than  those  of 
the  corresponding  nerves  to  which  they  are  afterwards  united. 
The  oculo-pupillary  sympathetic  branches,  finally,  spring 
from  the  spinal  cord,  by  the  roots  of  the  first  two  dorsal 
pairs,  in  a  manner  quite  independent  of  the  corresponding 
vaso-motors.  We  see  thus,  that  the  study  of  the  passage  of 
these  nerves  offers  unexpected  complications,  and  difficulties 
which  it  is  not  easy  to  remove  by  experiment,  their  course, 

12 


178  TEE  BLOOD  AND  ITS  CIRCULATION. 

according  to  Schiff,  differing  in  animals  of  the  same  kind, 
under  different  circumstances. 

As  the  vaso-motors  spread  into  the  arteries,  they  follow  an 
independent  course  in  certain  parts,  as  in  the  neck  and  head, 
where  the  sympathetic  nerve,  even  in  its  secondary  plexus,  is 
detached  from  the  nervous  system  which  presides  over  the 
organic  processes ;  in  other  cases,  their  arrangement  exactly 
resembles  that  of  the  arterial  branches  (abdominal  sympa- 
thetic) ;  or,  finally,  as  is  the  case  with  the  limbs,  they  unite 
and  are  lost  in  the  nerves  of  the  brachial  and  lumbar  plexus, 
etc.,  the  union  being  made  at  the  level  of,  or  at  a  certain 
distance  from,  the  plexus ;  in  the  case  of  the  sciatic  nerve,  a 
little  before  it  leaves  the  pelvis,  and  in  the  nerves  of  the 
arm,  at  the  level  of  the  brachial  plexus  (Claude  Bernard). 

The  modifications  caused  in  the  circulation  by  the  func- 
tions of  the  vaso-motor  nerves,  are  extremely  important  when 
considered  in  reference  to  the  phenomenon  of  secretion  and 
calorification  (see  animal  heat,  farther  on).  These  modi- 
fications should  be  also  closely  studied  in  regard  to  many 
pathological  phenomena.  Thus  fever  is  owing,  in  a  great 
measure,  to  a  derangement  of  the  vaso-motor  nerves  paralyz- 
ing the  vessels,  and  producing  a  change  in  the  regulation  of 
the  heat  of  the  body.  A  remarkable  disagreement  may  also 
sometimes  be  observed  between  a  local  disease  and  the  fever 
which  accompanies  it.  The  latter  may  break  out,  or  cease  sud- 
denly, by  a  modification  which  is  in  some  respects  dynamic 
(nervous  system),  while  the  disease  must  run  its  course 
through  all  the  phases  of  cellular  and  vegetative  growth 
(Hirtz). 

In  order  to  complete  the  history  of  the  vaso-motor  nerves, 
it  would,  finally,  be  necessary  to  review  the  numerous  thera- 
peutical applications  by  which  these  modifications  may  be 
produced,  but  we  will  mention  one  only  of  this  class  of 
medicaments,  —  digitalis  ;  this  substance  has  the  effect  of 
lowering  the  pulse  and  diminishing  heat,  and  is,  therefore,  a 
powerful  agent  against  fever,  the  pathological  physiology  of 
which  may  be  briefly  stated  in  these  few  words.  Besides 
retarding  and  regulating  the  motion  of  the  heart,  digitalis 
also  acts  on  the  peripheral  organs  of  the  circulation,  causing 
contraction  of  the  coats  of  the  arteries,  by  exciting  the  vaso- 
motor nerves  (Ackerman).  When  slackened  by  digitalis, 
the  pulse  becomes  stronger  and  fuller.  The  tension  of  the 
arteries  appears  to  increase,  and  the  special  power  of  this 


GENERAL   USES  OF  THE   CIRCULATION.  179 

remedy  seems  to  consist  in  its  restoring  the  contractility  of 
the  small  arteries  under  the  influence  of  the  vaso-motor 
nerves  proceeding  from  the  great  sympathetic.  Digitalis 
nmst,  therefore,  be  henceforward  considered  as  regulating 
the  circulation  by  means  of  an  exciting,  tonic  action,  and 
not  a  hyposthenisant  as  is  generally  supposed  (Ilirtz,  "Nouv. 
Diet,  de  Med.  et  de  Chirurgie"). 


IV.    General  Uses  of  the  Circulation. 

The  principal  purpose  of  the  circulation  is  to  produce 
rapid  currents  in  the  interior  of  the  tissues,  intended  to  sup- 
ply the  organs  with  the  materials  of  nutrition,  and  to  carry 
off  the  waste  resulting  from  the  changes  which  these  under- 
go, as  we  pointed  out  at  the  beginning  of  our  description  of 
the  organism.  These  changes  take  place  in  the  capillaries ; 
we  know  that  the  pressure  in  these  small  vessels  is  generally 
from  -^^  to  y^^  of  the  atmosphere,  and  this  pressure  appears 
very  fivorable  to  the  regularity  of  the  changes.  When  the 
pressure  is  diminished,  as  after  bleeding,  reabsorption  takes 
place ;  if,  on  the  contrary,  the  pressure  in  the  capillaries  is 
increased,  as  by  compression  or  ligature  of  a  vein,  the  exu- 
dation exceeds  the  normal  limits,  and  the  serum  of  the  blood, 
overflowing  into  the  tissues,  constitutes  what  is  called 
cedema.  Paralytic  dilatation  of  the  small  arteries  may  also 
produce  oedema  by  increasing  the  afflux  of  blood,  and,  conse- 
quently, the   pressure   in   the   capillaries.^      The   stings   of 

'  According  to  a  recent  communication  by  Ranvier  to  the  Aca- 
demic des  Sciences  (January,  1870),  vaso-motor  paralysis  is  the  most 
important  condition  in  the  production  of  oedema.  In  attempting 
to  produce  artificial  oedema  by  compression  and  obliteration  of  the 
veins,  Ranvier  was  surprised  to  find  that  the  ligature  never  caused 
eerous  infiltration  in  the  parts  situated  beyond  it. 

In  experimenting  on  rabbits  and  dogs,  he  tied,  first,  the  two 
jugular  veins  at  the  base  of  the  neck;  second,  the  femoral  vein,  at 
the  level  of  the  crural  ring;  third,  the  inferior  vena  cava.  In  none 
of  these  cases  did  oedema  ensue,  either  in  the  face  or  the  lower 
limbs;  while,  having  cut  the  sciatic  nerve  on  one  side,  thus  para- 
lyzing the  vaso-motor  nerves  of  the  limb,  in  a  dog  in  which  he  had 
tied  the  inferior  vena  cava,  he  found  that  considerable  oedema  fol- 
lowed on  this  side,  and  the  other  remained  in  its  normal  condition. 
The  same  phenomenon  was  repeated  in  several  experiments. 

It  is  true  that  the  sciatic  nerve  is  a  mixed  nerve,  containing  in 
the  same  covering  sensitive  fibres,  voluntary  motor  fibres,  and  vaso- 


180  THE  BLOOD  AND  ITS  CIRCULATION. 

insects  or  of  venomous  plnnts  (the  nettle),  produce  by  this 
mechanism  the  rapid  swelling  by  which  they  are  distin- 
guished. Beside  the  influences  of  changes  of  pressure,  we 
must  also  take  into  account  the  physiological  properties  of 
the  globules  in  the  vicinity  of  these  vessels,  for  we  know 
already,  and  shall  soon  see  more  particularly  (study  of  the 
epithelial  or  mucous  and  glandular  surfaces),  that  there  are 
certain  tissues  formed  of  globules  which  act  as  barriers  to  the 
passage  of  fluids  while  others  more  especially  assist;  in 
other  words,  the  tissues  near  the  capillaries  exercise  more  or 
less  attraction  to  the  contents  of  these  tissues. 

Beside  these  general  functions,  the  circulatory  system 
exhibits  s})ecial  arrangements  in  certain  parts,  indicating 
some  special  and  accessary  purpose ;  thus  the  vessels,  in 
some  organs,  have  to  perform  the  part  of  supplying  heat  as 
well  as  nutrition,  as  the  vessels  of  the  external  ear,  of  the 
face  in  general,  the  extremities  of  the  fingers,  and  the  integ- 
uments of  the  articulating  regions ;  these  vessels  are  much 
more  numerous  in  all  these  parts  than  the  simple  purpose  of 
nutrition  requires.  In  other  parts  the  capillaries  are  arranged 
with  a  special  view  to  absorption  or  exhalation,  as  those  of 
the  lung,  which  form  in  this  viscus  a  large  work  of  blood- 
vessels in  which  the  red  globules  become  impregnated  with 
oxygen,  while  the  serum  evolves  its  carbonic  acid. 

The  afilux  of  the  blood  has  also  a  mechanical  part  to  play, 
that  of  erection,  for  instance;  it  is  in  this  case  only,  that  we 
find  those  accessary  peripheral  hearts^  intended  to  increase 
the  tension  of  the  blood  in  the  organs  which  are  capable  of 
erection :  by  their  rhythmical  contraction  during  erection, 
the  bulbo-cavernous  and  the  ischio-cavernous  muscles  drive  to 
the  extremity  of  the  penis  the  blood  which  has  flowed  into 
the  bulb  of  the  urethra,  and  the  root  of  the  cavernous  bodies. 

The  movement  of  the  circulation  is  indispensable  in  order 
to  keep  the  blood  in  its  physiological  condition,  a  fluid  state ; 
not  that  the  motion  prevents  the  coagulation  of  the  blood ; 
on  the  contrary,  it  promotes  it,  and  it  is  by  beating  that  the 


motor  fibres.  But  Ranvier  had  satisfied  himself,  by  previous  ex- 
periments in  tying  the  inferior  vena  cava,  that  destruction  of  the 
sensitive  roots  and  of  the  voluntary  motor  roots  at  their  issue  from 
the  spinal  cord  was  followed  by  no  cedematous  phenomenon  in  the 
abdominal  region.  Paralysis  of  the  vaso-raotor  nerves  appears  thus 
to  be  the  cause  of  the  dropsy  which  takes  possession  of  the  limb 
which  has  undergone  section  of  the  sciatic  nerve. 


i 


GENERAL  USES  OF  THE  CIRCULATION.         181 

fibrine  is  extracted  from  the  blood;  but  the  movement  of  the 
circulation  brings  the  different  parts  of  the  mass  of  blood 
into  continual  contact  with  the  inner  coat,  the  endothelium 
of  the  vessels.  Among  the  more  or  less  well-defined  causes 
already  mentioned  (page  125),  influencing  the  coagulation 
of  the  blood,  the  least  disputed,  though  most  difficult  to  ex- 
plain, is  the  still  puzzling  influence  of  the  inner  coat  of  the 
living  vessels.  This  influence  was  pointed  out  by  Briicke : 
contact  with  the  limng  coat  is  a  powerful  obstacle  to  coagula- 
tion; the  fibrine  cannot  become  solid,  while  the  blood  is  cir- 
culating, and  while  each  of  its  particles  comes  constantly  in 
contact  with  the  living  coat. 

As  soon  as  the  circulation  ceases,  the  central  layers  of  the 
blood  current  have  a  tendency  to  coagulate :  examination  of 
the  manner  in  which  this  coagulation  is  produced,  constitutes 
the  study  of  clots  formed  after  death,  and  is  no  less  important 
to  the  physiologist  than  to  the  pathologist,  whom  it  teaches 
how  to  distinguish  recent  from  ancient  clots.  The  blood  in  a 
corpse  does  not  directly  coagulate  when  the  action  of  the  heart 
ceases ;  the  mechanism  by  means  of  w^hich  the  dying  arteries 
drive  their  contents  into  the  veins  (see  natural  form  of  the 
arteries,  P^ge  l'^3),  forms  still  a  kind  of  circulation,  prevent- 
ing this  coagulation :  in  a  corpse,  therefore,  clots  are  gener- 
ally found  only  in  the  veins. 

When  the  veins  of  a  corpse  are  gorged  with  blood,  which 
has  poured  in  from  the  arterial  system,  coagulation  begins  to 
take  place  in  the  central  layers,  because  the  most  distant  from 
the  coat ;  here  the  fibrine  coagulates  rapidly,  entangling  the 
red  globules  in  this  part  of  the  blood,  which  explains  the  fact 
that  the  centre  of  the  venous  clots  is  always  red  or  black, 
in  short,  appears  cruoric. 

From  20  to  24  hours,  at  the  least,  elapse  before  the  most 
peripheral  parts  of  the  contents  of  the  veins  are  completely 
coagulated  ;  here  the  influence  of  contact  with  the  living 
coat  is  still  felt.  It  rarely  happens  that  the  death  of  all  the 
anatomical  elements  coincides  with  the  general  death,  the 
last  breath  and  the  last  pulsation  of  the  heart ;  we  have  seen 
that  the  muscles  and  the  nerves  continue  excitable  long  after 
this,  and  that  the  epithelium  of  the  bladder  still  resists  the 
phenomenon  of  absorption  for  several  hours ;  we  shall  find 
that  the  vibratory  epitheliums  continue  their  movements 
during  from  8  to  10  hours ;  the  case  is  the  same  with  the 
endothellu7n  of  the  blood-vessels,  and  it  is  only  at  its  com- 
plete death,  at  the  end  of  20  or  24  hours,  that  coagulation  of 


182 


THE  BLOOD  AND  ITS  CIRCULATION. 


the  most  peripheral  layers  of  the  venous  blood  has  been 
accomplished  :  a  bloody  fluid  is  often  extracted  from  the 
vessels  of  a  corpse,  already  in  the  state  of  cadaveric  rigidity, 
which,  being  placed  in  a  vase  in  contact  with  the  aii*  soon 
coagulates,  almost  like  blood  taken  from  a  living  animal. 

Coagulation  in  the  corpse  taking  place  thus  slowly,  we 
have  here  all  the  conditious  favorable  to  the  separation  of 
the  fibrine  and  the  globules,  and  to  the  formation  of  a  hiffy- 
coat  (see  huffy-coated  bloody  p.  126).  The  vessels,  indeed, 
may  be  considered  as  forming  a  reservoir  of  a  complicated 
form,  in  which  during  coagulation  the  fibrine  and  globules 
m*e  placed  in  layers  according  to  their  weight,  the  globules 
in  the  inclined  parts,  the  fibrine  in  those  more  raised,  in  the 
form  of  colorless  clots:  whence  the  mixed  clots,  or  those 
formed  partly  of  cruoric  clots  (centre  and  inclined  parts  of 
the  coagulated  masses)  and  paitly  of  discolored  or  buffy- 
coated  clots.  In  the  latter,  as  in  the  buffy-coat  formed 
after  coagulation  in  a  vase,  are  found  a  large  number  of 
white  globules  (Fig.  55),  so  many,  sometimes,  being  joined 
together,  that  they  might  easily  be  taken  for  a  collection  of 
pus. 


Fig.  55.  —  Fiuiinous  clftt  witliout  red  globules.* 

The  arrangement  of  these  mixed  clots  is  determined  by 
tlie  position  of  the  body  after  death:  thus,  the  corpse  being 
generally  laid  upon  the  back,  the  clot  in  the  vena  cava  is 
colorless  in  the  vicinity  of  the  heart,  and  becomes  darker 
towards  the  lumbo-dorsal   region,  which  is  more  inclined, 

*  A  fJi.ff  Thin  fibrinous  layer,  showinj^  the  interlacing  of  the  striiE  of  the 
librin'ous  layer,  i.  k,  Leucocytes  nnited  witli  the  fibrine,  and  bleached  by  the 
action  of  wat'^r  (500  diam.)     (Robin,  "  Traits  du  Microscope.") 


GENERAL  USES  OF  THE  CIRCULATION.         183 

becoming  again  colorless  in  the  sacro-vertebral  angle,  which 
is  a  little  more  raised,  and  resuming  its  cruoric  appearance 
in  the  iliac  veins,  especially  in  the  inner  ones ;  the  clots  in 
the  pulmonary  veins  are  always  very  dark,  on  account  of 
their  inclined  position.  By  turning  the  corpse  over,  while 
these  clots  are  forming,  their  position  is  changed,  and  mixed 
clots  of  an  opposite  composition  obtained. 

It  is  plain  how  useful  and  important  these  facts  may  be,  in 
legal  medecine,  for  instance,  by  deciding  the  position  in 
which  a  corpse  has  lain  during  24  hours  after  death.  They 
are  all  the  result  of  that  singular  property  by  which  the 
internal  coat  of  the  vessels  prevents  coagulation. 

This  is  not  the  only  property  of  the  vascular  walls ;  it  is 
observed  that  coagulation  in  the  vessels  produces  a  clot,  but 
little  or  no  serum  is  found :  this  is  owing  to  the  fact  that 
when  the  arterial  coats  lose  their  properties  as  living  tissues, 
the  fluid  part  of  the  blood  predominates ;  either  because  these 
coats,  being  no  longer  living,  cannot  effect  those  natural 
changes  of  absorption,  etc. ;  or  because  the  separation  of  the 
fibrine  has  left  the  other  albuminous  elements  of  the  blood  in 
a  state  of  composition  favorable  to  their  exudation,  as  occurs 
in  the  living  body,  and,  by  a  similar  mechanism,  in  certain 
forms  of  cedema  and  albuminuria. 


PART   FIFTH, 


EPITHELIAL  GLOBULES  AND  EPITHELIAL 
SURFACES  IN  GENERAL. 


We  have  studied  the  nerve  globule,  which  by  its  prolonga 
tions  places  the  globular  elements  of  the  organism,  or  of 
their  derivatives,  in  relation  with  each  other  (reflexes)  ;  and 
the  muscle,  which,  obeying  the  motor  prolongations  of  the 
nerve  globule,  serves  to  modify  mechanically  the  relations 
between  the  different  parts  of  the  organism  to  each  other,  or 
to  the  outer  world ;  we  have  seen  that,  for  this  purpose, 
there  are  numerous  mechanical  apparatus  attached  to  the 
muscle  (bones,  tendons,  ligaments,  etc.) ;  we  have,  finally, 
studied  the  blood  globule,  and  the  blood,  which,  loaded  with 
the  new  materials  absorbed  by  certain  surfaces  of  the  organ- 
ism, carries  these  former  into  the  deeper  tissues,  while  it 
draws  to  the  excretory  surfaces  the  products  of  decomposi- 
tion and  of  the  interior  combustion  of  the  organism.  We 
have  now,  therefore,  to  study  the  physiology  of  these  sur- 
faces, that  is,  the  epithelial  globules. 

Anatomically  speaking,  the  epithelial  globule  is  already 
known  to  us ;  what  especially  distinguishes  it  is  its  relation 
to  the  free  surfaces  of  the  body;  its  surfaces  are,  in  fact, 
formed  of  membranes,  composed  of  a  more  or  less  close  pad- 
ding of  connective  and  elastic  fibres,  and  are  covered  by  an 
element  of  which  modern  anatomy  alone  has  conceived  the 
importance,  —  epithelium. 

It  was  long  believed  that  the  first  organ  which  appears  in 
the  embryo,  is  the  nervous  system.  Modern  histological 
research  has  proved  that  the  first  layer  of  blastoderm  is  of  an 
epithelial  nature :  this  layer,  in  its  subsequent  development, 
becomes  the  intestinal  epithelium,  the  first  organic  membrane 
which  distinguishes  the  individual.     The  importance  of  the 


GENERAL  ANATOMY  OF  TEE  EPITHELIUMS.    185 


epithelium,  particularly  that  of  the  digestive  organs,  is  thus 
shown  by  its  early  formation ;  its  dimensions,  in  the  embryo, 
are  immense.  We  find  that,  by  the  thickness  of  its  layers, 
it  blocks  up  the  opening  of  the  small  intestine  in  the  foetus, 
and  even  in  the  adult  it  is  sometimes  4  or  5  times  thicker 
than  the  membrane  which  supports  it. 

I.   General  Anatomy  of  the  Epitheliums. 

Anatomists  recognize  two  distinct  forms  of  epithelium, 
pavement  and  columnar  epithelium;  it  is  only  in  their 
extremes,  however,  that  they  differ  so  much,  there  being  inter- 
mediate forms  between  them.  The  principal  epithelium,  for 
instance,  that  which  forms  the  essential  parenchyma  of  the 
glands,  is  neither  the  pavement  nor  the  columnar  epithelium; 
it  is  a  kind  of  spherical  globule. 

The  membranes,  whose  free  surface  is  coated  with  epithe- 
lium, belong  to  two  categories :  1,  serous  membrane^  generally 
forming  closed  cavities ;  2,  integumentary  membrane  (either 
internal  or  external).  The  distinguishing  characteristics  ob- 
served in  these  membranes  are  dependent  on  the  nature  of 
their  epithelium. 

A.  Serous  Membrane. 

The   class  of  epithelium   spread   on   the   surface   of  the 
serous  membranes,  is  the  pave- 
ment form  (Fig.  56,  A).     It  is  ^ 
generally  a  single  layer  of  cells    CsZr'^~:r'~^~ir~9~7r-^~\:^ 
which,  in  consequence  of  recip- 
rocal deformation  (being  crowd-     r-c--r-T^r>r->v---v-^->-r--r-~Y->r 
ed  together),  have  flattened  into      \M%S^H%?[^EEI9 

angular,  polygonal  disks  :  such     '  " 

is  the  epithelium  of  the  abdom- 
inal serum ;  the  case  is  the  same 
with  that  of  the  pericardium,  of 
the  arachnoid  membranes,  and  of 
all  the  serous  membranes  called 
visceral.  The  epithelium  which 
lines  the  inner  surface  of  the 
blood-vessels,  and  the  cavities  of  the  heart  (endocardium)  is 
also  of  this  kind.  The  epithelium  covering  the  articulating 
cavities  is  also  pavement,  but  composed  of  several  layers; 

*  A,  Pavement  epithelium.  B,  Columnar  epithelium.  C,  Stratified  epithe- 
lium. 


woTorofo/o)©  lo  1  o\oToro/3r3i 


wmE)mmmmmmm 


Fig.  56. 
Various  forms  of  epitheliums.* 


186  EPITHELIAL   GLOBULES. 

there  are,  beside, gaps  in  this  epithelial  casing  (synovial),  where 
the  cartilages  come  into  contact,  and  where  there  is,  conse- 
quently, the  strongest  pressure.  The  opinion  can  no  longer 
be  held  that  the  fibrous  substratum  of  the  serous  membrane 
alone  ceases  to  occur  at  the  level  of  the  articulating  cartilages, 
while  a  layer  of  epithelium  remains  on  these  articulating 
(cartilaginous)  surfaces.  The  articulating  surfaces  are  closed 
cavities,  but  their  whole  inner  surface  is  not  lined  with  epi- 
thelium. 

B.  Integumentary  Membranes. 

Many  organisms  possess  only  one  external  integument; 
this  is  the  case  with  vegetables.  But  animals,  under  their 
cutaneous  surfaces,  have  internal  surfixces,  communicating 
with  the  exterior ;  these  are  mucous  membranes. 

a.  Maternal  Integuments.  —  The  epithelium  of  these  sur- 
faces is  composed  of  numerous  layers :  on  the  surface  are 
found  flattened  cells,  while  globular  forms  prevail  in  the 
deeper  layers ;  these  latter  elements  exhibit  those  signs  of 
life  which  characterize  the  epitheliums ;  in  fact,  what  is  com- 
monly called  epidermis,  the  most  superficial  layer  of  the  skin, 
is  not  living  epithelium,  but  a  dead  body,  a  horny  substance 
as  impermeable  as  India-rubber.  But  below,  is  found  a  soft 
succulent  membrane,  which  has  all  the  features  of  the  epi- 
theliums of  the  mucous  membranes,  and  was  formerly  called 
MalpigMs  net  (rete  malpighianum)  ;  this,  properly  sj)eaking, 
constitutes  the  living  epidermis :  it  forms  a  continuous  cov- 
ering to  the  surface  of  the  dermis. 


Fig.  57.  —  Columnar  epithelium,  with  vibratory  cilia.* 

h.  Internal  or  m^ucous  Integuments.  —  All  the  sub-dia- 
phragmatic part  of  the  intestinal  canal,  the  beginning  of  the 
trachea  and  of  the  genital  organs,  and  their  course  as  far  a8 

*  a,  Body  of  the  cell3.  c,  Cilia.  J,  Molecules  floating  in  the  ambient  fluid, 
and  driven  by  the  cilia  in  the  direction  of  the  upper  an'ow,  in  which  direction 
they  are  erect,  while  in  that  of  the  lower  arrow  they  appear  bent.    (Valentin.) 


GENERAL  ANATOMY  OF  THE  EPITHELIUMS.    187 

the  internal  genital  organs,  properly  so  called,  exhibit  the 
features  of  the  external  integuments,  if  the  essential  element 
of  the  raucous  membrane,  epithelium,  be  taken  into  account ; 
the  pavement  form  being  always  found  on  the  surf  ice,  and 
the  globular  forms  beneath.  But  if  we  penetrate  these 
organs  more  deeply,  we  find  that  the  epithelium  changes  its 
form,  and  becomes  cylindrical.  Thus,  in  the  epithelium 
which  covers  the  uterus,  the  spermatic  organs,  the  stomach, 
the  intestine,  and  the  trachea  below  the  vocal  cords,  we 
recognize  certain  general  features,     .  i  g 

such  as  the  cylindrical  or  conical  ^  ^ 

form  of  cells,  and  the  constant 
presence  of  the  nuclei  (Fig.  58)  ; 
and  also,  characteristic  peculiari- 
ties, of  which  the  most  im])ortant 
is  the  existence  in  some  of  them 

of    ciliated    prolongations^    with    Fig.   58.  —  Colnmnar  or  cylindrical 

which  their  free  surfaces  are  pro-      cells  of  the  intestinal  mucoua 

.  ,     ,     ,        .  .         1       •!  membrane.    (Robin.) 

vided,  havmg  a  contmual  vibra- 
tory movement,  w^hich  lasts  all  through  life :  this  movement 
is  apparent,  even  some  time  after  the  death  of  the  general 
organism  (cessation  of  the  circulation  and  innervation)  these 
are  the  vibratile  colurnnar  epitheliums  (Fig.  57). 

The  movements  of  the  vibratile  cilia  of  the  cells  are 
among  the  most  curious  phenomena  presented  by  the  epi- 
theliums :  the  movement  of  the  free  cells,  furnished  in  some 
cases  with  several  cilia  which  assist  them  in  locomotion,  are 
of  the  same  kind ;  we  shall  see  further  on  that  the  sperma- 
tozoids  are  elements  of  this  class;  these  elements  become 
more  numerous  as  we  descend  the  scale,  until,  at  length,  we 
find  them  representing  organisms  which  are  endowed  with  a 
perfect  individuality. 

The  cells  having  vibratile  cilia  are  always  cylindrical  in 
the  higher  animals:  in  the  mollusks  and  in  beings  of  a  still- 
lower  order,  they  appear  under  every  possible  form.  It  is 
remarkable  that  no  epithelium  with  vibratile  cilia  has  been 
observed  among  the  articulata  (insects).  The  cilia  which 
spring  from  the  base  of  the  cells  are  generally  fine  and 
straight,  but  they  are  sometimes  so  bulky  and  their  motion 
so  extended,  that  the  glittering  waves  which  they  produce 
on  the  surface  of  the  mucus  may  be  seen  with  the  naked 
eye,  as  on  the  branchial  lamellae  of  the  mollusks.  On  exam- 
ining these  movements  with  a  powerful  magnifying  lens,  w^e 
find  that  the  cilia  either  bend  in  the  shape  of  a  hook,  or  perform 


188  EPJTnELlAL   GLOBULES, 

a  circuraductory  movement  in  such  a  manner  as  to  describe 
a  sort  of  funnel,  or  else  curve  like  a  whip-lash  {flagellum 
of  the  infusoria,  tail  of  the  spermatozoids),  or  simply  oscillate, 
however,  always  more  towards  one  side  than  the  other,  so 
as  to  produce,  at  length,  in  the  fluid  or  mucus  in  which  they 
are  immersed,  a  progressive  movement  which  is  always  in 
the  same  direction  (Fig.  57,  upper  arrow).  Their  rapidity 
of  motion  renders  observation  of  them  often  extremely  diffi- 
cult, as  they  make,  at  times,  from  200  to  250  movements  iu 
a  second. 

When  examined  with  a  less  powerful  mngnifier,  the  result 
of  these  movements  gives  the  epithelial  surface  in  which  they 
take  place  the  aspect  of  a  field  of  wheat  moved  by  the  wind, 
or  of  a  river  glistening  in  the  sun.  Small  bodies  (coal-dust), 
placed  on  this  surface,  move  upon  it  in  a  decided  direction. 
These  phenomena  may  be  easily  observed  in  the  frog :  in  the 
mucous  of  its  trachea  the  motion  is  seen  to  proceed  from  the 
lower  to  the  upper  part,  that  is,  from  the  lung  to  the  mouth ; 
in  the  pharyngeal  and  (esophageal  mucous,  on  the  contrary, 
it  proceeds  from  the  mouth  to  the  stomach.  These  currents 
are  explained  by  the  fact  that  the  vibrations  of  these  fila- 
ments are  made  in  a  peristaltic  form ;  that  is,  in  those  of  the 
cesophagus,  for  instance  (in  the  frog),  the  movement  or  undu- 
lating wave  begins  in  the  cilia  of  the  cells  of  the  tongue,  and 
continues  in  those  which  are  situated  lower  in  the  pharyngeal 
duct ;  the  nervous  system,  meanwhile,  has  nothing  to  do  with 
the  co-ordination  of  these  movements,  and  on  a  piece  of  de- 
tached mucous  we  may  by  the  regular  direction  of  the  move- 
ment even  distinguish  the  buccal  extremity  from  the  oeso- 
phageal extremity  of  the  fragment;  we  see  the  cilia,  also, 
fall  and  rise  ten  or  twelve  times  in  a  second,  and,  like  oars, 
hold  out  their  thin  edge  as  they  rise,  and  strike  with  their  flat 
surface  as  they  sink,  by  which  means  they  advance.  (The 
process  may  be  reversed,  according  to  the  peculiarity  of  the 
animal  under  consideration.) 

If  the  surface  be  scraped,  and  the  cells  detached  from  it, 
we  find  that  the  cilia  with  which  they  are  still  provided, 
continue  to  move,  but  in  an  irregular  manner:  while  the  cell 
floating  in  the  fluid,  being  displaced  by  the  movements  of 
the  cilia,  eddies  about  at  random,  Michael  Foster  com- 
pares it,-  under  these  circumstances,  to  "  a  boat  without  a 
rudder,  manned  by  mad  sailors."  It  is  thus  probable  that, 
when  the  cells  are  in  their  accustomed  place,  the  movements 
of  the  vibratile  cilia  (those  of  the  mouth  in  their  relation  to 


1 


GENERAL  ANATOMY  OF  THE  EPITHELIUMS.     189 

those  of  the  pharynx  in  the  frog),  by  their  contact  cause 
those  next  to  them  to  enter  into  action ;  and  thus,  by  the 
mechanism  of  constantly  succeeding  impulses,  this  wonderful 
chain  of  influences  is  produced. 

If,  however,  the  cilia  be  detached  from  the  cell  to  which 
they  belong,  they  immediately  cease  to  move :  their  life  is, 
thus,  evidently  bound  up  with  that  of  the  cell,  and  especially 
of  the  protoplasm  filling  the  cell  of  which  they  form  a  part ; 
Eberth  and  Marchi,  indeed,  have  discovered  that,  in  the 
mollusks,  the  vibratory  cilia  penetrate  the  plane  with  which 
the  free  base  of  the  cell  is  furnished,  and  come  in  close  con- 
tact with  the  cellular  contents ;  and,  by  means  of  the  modi- 
fications which  the  vibratile  cilia  undergo  at  the  beginning 
of  a  coryza,  Ranvier  has  shown  that  this  important  feature 
of  structure  is  found  in  man  also. 

Different  circumstances  tend  to  modify  the  vibratile 
movements  of  these  epitheliums:  they  have  been  studied 
with  great  minuteness  by  Michael  Forster  and  by  Calli- 
burces  in  the  oesophagus  of  the  frog.  They  are  checked 
by  anaesthetics  (ether,  chloroform),  but  regain  their  vi- 
vacity on  withdrawal  of  the  vapor;  according  to  Michael 
Forster,  the  absence  of  oxygen  appears  to  paralyze  them 
as  if  by  producing  a  state  of  asphyxia.  Acids  render  them, 
immovable,  but  alter  their  structure;  the  movements  may, 
however,  be  resumed,  if  the  acid  be  much  diluted  and  neu- 
tralized by  an  alkaline  solution  ;  these  alkaline  solutions  are 
very  effectual  in  accelerating  the  motion  (acids  and  alkalies 
produce  an  exactly  similar  effect  upon  the  sperm atozoids). 
A  low  temperature  !<lackens  their  motion,  whilst  a  high  one 
increases  it ;  in  the  hibernating  animals  the  movements  ap- 
pear to  cease  during  hibernation  (?).  No  poison  has  any 
effect  upon  them,  unless  the  animal  be  poisoned,  or  the  poi- 
sonous substance  placed  directly  on  the  epithelial  surface.^ 

^  A  curious  fact  has  been  brought  to  the  notice  of  the  Ameri- 
can editor.  The  American  black  bear,  which  is  a  good  illustra- 
tion of  a  hibernating  animal,  cannot  eat  food  in  winter  with 
impunity.  Two  bears  were  kept  during  one  winter  mider  obser- 
vation. As  in  their  natural  abode  they  went  to  sleep  on  the  first 
appearance  of  cold  weather.  Two  or  three  times  they  were  easily 
aroused  from  their  sleep,  and  during  one  of  these  occasions  one  of 
th(?m  was  induced  to  take  a  very  small  portion  of  simple  food. 
During  the  next  two  or  three  days,  though  asleep  most  of  the  time, 
it  sickened  and  died.  The  other  bear,  who  was  not  allowed  to  be 
disturbed  until  the  opening  of  spring,  recovered  his  activity;  but, 


190  EPITHELIAL   GLOBULES. 

These  epitheliums  with  vibratile  cilia,  which  were  first 
studied  in  the  lower  animals  by  Hunter  Sharpey  and 
Ehrenberg,  have  been  since  discovered  in  different  mucous 
coverings  of  the  vertebrated  animals, 
and  the  mammifera.  In  the  adult 
man  they  are  found  in  the  nasal  fos- 
sae, the  trachea,  the  large  bronchi,  the 
eustachian  tube,  the  membrana  tym- 
pani  (the  inner  surface  of  the  tympanic 
membrane  excepted)  the  nasal  canal, 
the  deferent  canals,  the  canal  of  the  epi- 
didymis, and  the  canals  of  the  seminif- 
erous cones;  also  in  the  Fallopian  tube 
and  the  uterus  in  woman.  (Fig.  59.) 
In  the  foetus  they  are  also  found  in  the 
canal  of  the  spinal  cord,  and  the  cere-  Fig.  59.  —  Ceiis  of  the  utems 
bral  ventricles  which  follow  it.  S^SrS""- r«m^ 

In  the  other  vertebrated  animals  "^"^'^9'ni«'„et  Physioiogie 
the  epitheliums  are  more  widely  dif- 
fused, becoming  still  more  numerous  in  the  non-vertebrated 
animals  (the  mollusks  especially),  in  which  they  sometimes 
line  the  whole  external  integument  and  the  mucous  membrane 
of  the  digestive  tract. 


n.    General  Physiology  of  the  Epitheliums.  —  Lymphatic 

System. 

A.  T'he  epitheliums  preside  over  the  interchanges  of  nutri- 
tion  at  their  free  surfaces. 

We  have  already  seen  in  our  general  sketch  of  the  organ- 
ism that  thie  epitheliums  manage  the  phenomena  of  inter- 
changes with  the  outside,  and  that,  in  this  respect,  they  are 
divided  into  three  classes :  those  which  are  impermeable,  and 
offer  no  passage  either  from  the  outside  to  the  inside,  or  tjie 
opposite ;  those  which  allow  a  passage  from  the  exterior  to 
the  interior  (absorption) ;  and  those  in  which,  on  the  other 
hand,  the  passage  is  from  the  interior  to  the  exterior  (se- 
cretion). 

contrary  to  what  is  generally  believed,  was  not  perceptibly  thinner 
than  in  the  autumn.  In  fact,  the  New  England  hunters  say  that 
the  amount  of  grease  derived  from  these  animals  in  the  mouth  of 
May  is  very  considerable,  even  if  the  preceding  winter  has  been 
l(»ng  and  severe. 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS.    191 

In  order  to  perform  these  latter  functions,  the  epithelial 
surfaces  extend  as  far  as  possible,  vegetate,  and  form  projec- 
tions, for  the  purpose  of  absorption ;  as  well  as  internal  vege- 
tations or  glands^  for  the  purpose  of  increasing  the  number  of 
secreting  elements. 

These  forms  of  vegetation  may  have  still  another  object ; 
the  epithelial  surfaces  being  the  only  points  at  which  the 
peripheral  extremities  of  the  sensitive  or  centripetal  nerves 
(;ome  in  contact  with  the  outer  world,  certain  epithelial 
shoots  (papillae)  are  intended  to  increase  and  facilitate  these 
connections ;  this  is  the  origin  of  the  organs  of  the  senses. 
These  shoots,  whose  business  it  is  to  perfect  sensation,  may 
not  only  be  produced  outside,  like  the  papillae  in  general, 
but  also  in  the  very  depths ;  and  one  of  the  most  important 
parts  of  the  eye,  for  instance  the  crystalline,  is  only  a  deep 
budding  {boui'geonnement)  of  the  epidermis. 

We  must,  therefore,  study  the  internal  and  external  integ- 
uments, first  in  regard  to  their  permeability,  that  is,  absorp- 
tion and  secretion,  and  then  to  their  sensibility.  We  will 
begin  with  the  epithelium  of  the  digestive  tube,  and  of  the 
respiratory  apparatus,  which  are  especially  appointed  to  ab- 
sorb the  fluid  and  gaseous  materials,  and  are  the  seat  of 
numerous  secretions  and  exhalations.  We  will  then  exam- 
ine the  cutaneous  surface,  whose  functions  are  principally 
those  of  secretion  and  sensibility.  Here  the  organs  of  the 
penses  will  come  in,  being,  for  the  most  part,  attached  to  the 
cutaneous  system  (sight,  hearing,  touch),  or  to  the  beginning 
of  the  digestive  or  respiratory  organs  (taste,  smell). 

In  all  the  general  organs,  the  functions  of  the  epithelium 
are  most  important  and  essential,  but  they  cannot  be  per- 
formed without  the  assistance  of  numerous  other  organs, 
whose  part  is  either  mechanical  (muscles)  or  nervous  (reflex 
influences). 

Nothing  shows  the  importance  of  tile  epitheliums  so  well 
as  a  consideration  of  the  part  which  they  play  in  diseases  of 
the  surfaces  covered  by  them.  Diseases  of  the  epithelium 
prevail,  in  fact,  beyond  all  those  of  the  surface  which  it  covers. 
For  instance,  pseudo-membranous  inflammation  of  the  re- 
spiratory tree  consists  principally  in  hypertrophy  of  the 
tracheal  epithelium,  and  these  croup-membranes  are  found  in 
numerous  transient  forms,  in  which  the  primitive  form  may 
be  discovered,  proving  that  they  are  only  impaired  or  degen- 
erated epithelium.     The  same  fact  is  observed  in  the  deep- 


■ 


192  EPITHELIAL   GLOBULES. 

seated  epithelium  of  this  system,  the  epithelium  of  the  pul- 
monary vesicles  :  pneumonia.,  or  inflammation  of  the  lungs,  is 
only  an  alteration  of  the  epithelium  of  the  vesicles;  these  cavi- 
ties are  often  found  filled  with  fragments  of  epithelium  to  such 
an  extent  that  the  air  is  entirely  excluded.  Tubercle  is  hyper- 
trophy followed  by  a  sort  of  mummified  deposit.,  formed  by  the 
epithelium.  This  deposit  softens  after  a  time,  —  a  chemical 
change  similar  to  that  observed  in  the  work  of  the  glands. 

In  the  intestinal  canal,  the  pathological  condition  offers  us 
also  some  important  glimpses  into  the  role  of  the  epithelium. 
Dysentery  is  a  croupous  inflammation  of  this  membrane,  its 
morbid  product  being  degenerated  epithelium  of  the  large 
intestine.  An  intestinal  loop  in  strangulated  hernia  also 
exhibits  croupous  transformation,  and  this  same  epithelium 
also  plays  the  chief  part  in  degeneration  of  the  mucous 
coat. 

The  case  is  the  same  with  the  skin:  physiologists  for  a 
long  time  attached  no  importance  to  the  epidermis,  regarding 
it  as  a  secretory  product  of  the  dermis,  and  yet  it  is  the 
e[)idermis  which  is  principally  affected  in  diseases  of  the  skin, 
and  by  far  the  greater  number  of  the  diseases  called  derma- 
tose  are  only  epidermatose.,  deterioration  of  the  cutaneous 
epithelium  or  epidermis.  In  producing  certain  dermatoses 
artificially,  we  place  the  germ  of  the  virulent  malady  which 
we  wish  to  ingraft,  not  in  the  dermis,  but  on  the  surface,  or 
in  the  depths  of  the  epidermis.  In  these  layers,  too,  the  first 
signs  of  most  cutaneous  diseases  appear;  these  are  always,  at 
least  in  the  commencement,  only  degeneration  of  the  normal 
product.  The  elements  of  e/>*^Ae/ia/  cancerous  tumors.,  how- 
ever, are  in  themselves  normal;  what  renders  the  product 
morbid  in  this  case  is  hypertrophy  of  these  elements,  an  in- 
crease in  number  and  size.  Ttie  same  remark  applies  to 
what  are  called  benign  tumors,  to  corns  and  callosities^ 
which  are  all  abnormal  developments  of  epitlermis;  these, 
meeting  with  some  resistance  on  the  surface,  penetrate  the 
interior,  breaking  through  the  dermis,  the  aponeuroses,  the 
tendons,  and  the  muscles,  until  they  reach  the  bone.  Tl^ose 
tumors  in  the  integuments,  called  sebaceous  wens,  which  are 
at  first  only  as  large  as  the  point  of  a  pin,  and  afterwards 
often  attain  considerable  size,  are  also  accumulations  of 
epithelial  degeneration. 

The  vitality  and  importance  of  the  epithelium  are  not  less 
striking  when  we  examine  that  which  lines  the  serous  mem- 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS.    193 

brane;.m  acute  effusion  of  the  peritoneum  hypertrophy  of 
the  epithelium  of  the  serous  membrane  takes  place,  occasion- 
ing, exactly  as  in  the  case  of  the  mucous,  the  formation  of 
false  membranes ;  also,  chronic  effusion,  when  not  produced 
by  mechanical  causes,  will  be  generally  found  to  be  the  result 
of  deterioration  of  the  epithelium.  When  medicines  are 
given  to  thicken  the  blood  and  excite  the  activity  of  certain 
organs,  if  their  effect  is  to  diminish  the  quantity  of  fluids  in 
the  body,  they  generally  fail  of  their  purpose ;  and  yet,  ac- 
cording to  physical  laws,  the  effusion  ought  to  be  reabsorbed. 
In  order  to  bring  about  this  result,  the  vitality  of  the  epi- 
thelium must  be  modified,  by  the  introduction  of  irritating 
substances  (as,  for  instance,  in  vaginal  effusions).  On  the 
other  hand,  the  application  of  physical  laws  to  the  functions 
of  the  pleura  would  occasion  the  formation  of  a  space 
between  its  two  folds  and,  consequently,  of  a  constant  liquid 
effusion  between  them :  this  effusion  takes  place  only  in 
pathological  conditions  of  the  serous  membrane,  that  is,  of  the 
epithelium  which  covers  it;  for  in  the  normal  state  this 
globular  layer  prevents  any  passage  of  fluid  and  any  exhala- 
tion from  within  outwards,  exactly  as  the  epithelium  of  the 
bladder  prevents  any  passage  from  without  inwards,  or 
absorption. 

We  may  conclude,  from  all  this,  that  the  general  property 
of  the  epithelial  globules  is  to  choose  their  materials,  to 
borrow  certain  elements  from  the  surrounding  mediums,  and 
reject  others.  We  shall  see  that  the  epithelium  of  the  blad- 
der repels  fluids  generally,  without,  however,  being  imper- 
meable in  the  proper  sense  of  the  word ;  it  is  impermeable 
by  election,  for  no  doubt,  the  urine  may  be  concentrated  in 
the  bladder,  but  the  water  alone  is  absorbed  without  passage 
of  the  dissolved  matter.^  In  the  intestinal  canal  we  find  that 
the  presence  of  certain  substances,  as  a  solution  of  sugar  or 
of  albumen,  produces  no  effect  on  the  epithelial  globule,  but 
that  it  enters  immediately  into  action  if  these  same  sub- 
stances be  modified  or  accompanied  by  the  gastric  juice. 

The  epitheliums,  in  short,  are  essentially  living  elements, 
as  is  proved  by  the  metamorphoses  and  functions  found  to 
exist  in  the  whole  series  of  phenomena  which  we  have  gone 
through. 

^  See  J.  C.  Susini,  "  De  I'lmperm6abilit6  de  I'Epith^lium  vesi- 
cal."    Thdse  de  doctorat,  Strasbourg,  18G7,  No.  30. 

13 


194  EPITHELIAL   GLOBULES. 

B.  The  lymphatic  system  considered  as  an  adjunct  to  the 
epithelial  functions. 

If  the  epitheliums  are  essentially  living,  they  must  and  do 
undergo  continual  changes.  Beside  the  young  cells  we  ought 
to  find  old  cells,  and  numerous  fragmentary  remains  of  the 
same;  we  may  be  sure  that  every  epithelial  globule  which 
exists  has  been  in  its  place  only  a  short  time,  and  will  soon 
disappear  to  make  room  for  another;  its  fundamental  char- 
acter is  its  ephemeral  existence.  This  fall,  this  constant 
change  of  the  epithelial  cells  is  really  the  means  by  which 
some  of  them  fulfil  their  functions :  thus  the  epitheliums 
of  the  glandular  culs-de-sac  are  destined  to  fall  continually 
into  deliquium,  and  thus  constitute  the  phenomenon  of  secre- 
tion.^ 

Apart  from  the  glands,  however,  the  fall  of  the  epitheliums 
is  not  a  function,  but  simply  a  result  of  their  existence.  In 
the  epidermis  which  covers  the  cutaneous  surface,  this  fall 
takes  place  under  the  form  of  furfuraceous  desquamation, 
that  is,  small  horny  scales  (a  collection  of  old,  dried-up 
epidermal  cells). 

In  the  mucous  membranes  desquamation  takes  the  form 
of  a  thick  ropy  fluid  product,  mucus^  which  has  given  its 
name  to  this  large  class  of  membranes.  The  mucus  is  less 
abundant  in  the  normal  than  in  the  pathological  condition, 
in  which,  we  might  say,  the  life  of  the  cells  is  suddenly  closed. 
It  is  a  hyaline  elastic  substance,  resembling  the  exterior  of 
the  eggs  of  the  batrachians,  insoluble  in  water,  coagulable  by 
acids,  but  easily  dissolved  in  alkaline  fluids;  the  application 
of  an  alkali  to  the  epithelial  membranes  has  the  effect  of 
dissolving  the  cellular  elements  under  the  form  of  mucus. 
The  chemical  composition  of  the  mucus  is  nearly  the  same  as 
that  of  albumen  ;  indeed  the  albumen  of  the  white  of  eggs  is 
only  mucus  of  the  genital  organs  of  the  bird. 

The  so-called  mucous  glands  generally  secrete  fluids  which 
are  very  tenuous,  and  miscible  with  water,  and  thus  differ 
greatly  from  the  mucus ;  the  latter  is  not  the  product  of  any 
ppecial  gland,  but  is  the  result  of  the  desquamation  and 
fusion  of  the  epithelium ;  but  this  shows  that  we  may  expect 
to  meet  with  all  the  transitions  between  the  mucus  properly 
BO   called,   and  the  various  products   of  special  secretions 

*  See  V.  Billet,  "  Generalites  sur  les  secretions."  Th^se  do 
doetorat,  Strasbourg,  18G8,  No.  129. 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS,    195 

(between  the  buccal  mucus  and  the  saliva,  for  instance). 
The  serosities,  found  more  or  less  abundantly  in  the  serous 
cavities,  are  produced  in  this  way  ;  the  synovia  is  the  result 
of  fusion  of  the  epithelial  articulating  membrane ;  in  order 
to  multiply  the  surfaces  on  which  this  fusion  takes  place,  the 
epithelium  of  the  serous  membranes  has  a  great  tendency  to 
vegetate,  and  thus  are  formed  the  epiploic  appendages  of  the 
peritoneum  and  the  synovial  fringes  of  the  articulating  cavi- 
ties. The  fluid  produced  by  these  surfaces  serves  to  lubri- 
cate them ;  and,  as  it  is  observed  that  the  serous  cavities  show 
a  tendency  to  disappear  when  they  cease  to  be  the  seat  of 
motion,  we  may  infer  that  their  presence  is  a  certain  sign  of 
the  existence  of  movements  between  the  surfaces  which  they 
line :  therefore  there  must  be  movements,  though  they  are 
hardly  perceptible,  between  the  dura-mater  and  the  arach- 
noid, these  two  membranes  being  lined  by  a  similar  epithe- 
lium to  that  of  the  serous  membranes. 

All  the  waste  of  the  epitheliums  cannot,  like  the  epidermal 
scurf  or  the  mucus,  be  carried  to  the  exterior,  or  into  the 
cavities,  like  the  synovia  which  is,  however,  partly  reab- 
sorbed. Besides,  to  carry  off  the  waste  part  of  the  cells  which 
are  placed  in  the  deeper  layers,  a  special  apparatus  is  needed; 
this  is  supplied  by  the  oj'igin  of  the  lymphatic  system.  The 
lymphatic  apparatus  is  composed  of  a  -system  of  vessels, 
which,  if  brought  together  in  a  diagram  similar  to  that  of  the 
blood-vessels,  exhibits  the  form  of  a  cone  the  summit  of 
which  joins  the  venous  system  (thoracic  duct  and  great 
lymphatic  vein  connecting  with  the  subclavians),  while  the 
base  (capillaries)  is  in  contact  with  the  epithelium  (Fig. 
60).  The  origin  of  the  lymphatic  capillaries  is  still  little 
known ;  but  it  is  probable  that  their  primitive  network  is  so 
superficial  that  the  base  of  the  lymphatic  cone  may  be  con- 
sidered as  closed  by  the  epithelial  membranes  ;  ^  thus,  when 
any  substance  is  placed  in  the  skin,  it  is,  as  it  were,  placed 
in  the  origin  of  the  lymphatic  system,  whence  its  rapid 
absorption ;  in  short,  it  is  inoculated,  and,  mixing  with  the 
1}  mph,  flows  with  it  into  the  circulating  current.   The  lymph, 

^  Lately,  however,  lymphatic  spaces  have  been  discovered 
situated  around  the  smaller  capillaries,  and  hence  have  been  called 
perivascular  spaces.  These  may  be  considered  as  the  origin  of  the 
lymphatic  system.  These  perivascular  spaces,  at  first  haviug  no 
limiting  membrane,  gradually  coalesce,  and  form  a  small  lymphatic 
vessel  having  a  true  limiting  membrane.     [Am.  ed.] 


196 


EPITHELIAL   GLOBULES. 


).  —  Diagram  of  the  lym- 
phatic system.* 


or  contents  of  the  lymphatic  vessels,  is  a  nearly  colorless  fluid, 
resembling  in  appearance  the  serous  fluid  of  a  blister,  and 
holding  in  suspension  a  large  num- 
ber of  white  globules  similar  to 
those  of  the  blood. 

The  lymph  which  is  found  in  all 
the  lymphatic  vessels,  and  the  chyle^ 
found  only  in  that  part  of  the  lym- 
phatic system  belonging  especially 
to  the  digestive  organ  (see  diges- 
tion) are  not  two  such  difierenl 
fluids  as  one  might  suppose  at  first 
sight,  and  as  ancient  physiologists 
considered  them  {lacteal  vessels  of 
Aselli  and  Pecquet;  serous  vessels 
of  Olaiis  Rudbeck).  Both  contain  the  same  elements,  and  the 
diff'erence  between  them  is  of  quantity  only,  not  quality;  the 
difi*erence  is,  besides,  only  momentary  ;  after  digestion,  or  at 
the  moment  when  absorption  takes  place,  the  mesenteric  lym- 
phatic vessels  (chyliferous)  contain  a  larger  quantity  of  the 
absorbed  elements,  especially  the  fats ;  we  must  also  add 
that  in  birds,  owing  to  certain  peculiarities  in  the  mechanism 
of  absorption  (CI.  Bernard),  the  difference  between  the  con- 
tents of  the  lymphatic  vessels  of  the  mesentery  and  those  of 
the  other  parts  of  the  body  seems  to  disappear. 

The  quantity  of  lymph  contained  in  the  lymphatic  vessels 
(lymphatic  cone,  Fig.  60),  and  poured  into  the  blood  system, 
varies  greatly,  according  to  the  state  of  repose  or  activity  of 
the  organs  from  which  it  proceeds ;  ^  thus  if  a  lymphatic  fis- 
tula be  made  in  the  neck  of  an  animal,  in  order  to  obtain  the 
flow  of  lymph  from  the  head,  we  observe  that  the  fluid  flows 
much  more  abundantly  during  mastication,  than  during  re- 


^  This  is  probably  due  to  the  fact  that  by  the  acti\nty  of  the 
muscles  the  perivascular  spaces  are  alternately  contracted  and  en- 
larged, setting  in  motion  the  lymph  towards  the  larger  lymjjhatic 
trunks.  This  current  is  further  facilitated,  or  prevented  fiom  a 
backward  flow,  by  the  valves  placed  all  along  the  lymphatic  vessels. 
These  valves  are  so  arranged  that,  when  thrown  out,  the  fluid 
passes  in  a  direction  from  the  periphery  to  the  centre.     [Am.  ed.] 


*  E,  E,  E,  Epithelial  surfaces,  base  of  the  lymphatic  cone  L,  L,  L ;  this  cone 
is  connected  at  its  summit  with  the  venous  cone  Vn.  Ai%  Arterial  cone.  V, 
Left  Ventricle.  Y\  Right  ventricle.  O,  Left  auricle.  O',  Ilight  auricle.  S  P, 
Pulmonary  system. 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS.     t97 

pose  ( Colin). ^  Of  course,  a  still  greater  cTifference  is  observed 
in  the  lymph  which  comes  from  the  intestines,  in  proportion 
as  the  animnl  is  fasting,  or  in  the  midst  of  absorption  of  the 
products  of  digestion. 

When  the  lymph  docs  not  contain  much  fat,  it  is  a  fluid 
slightly  opalescent,  having  a  characteristic  odor  resembling 
that  of  the  spermatic  fluid,  and  recalling  the  special  odor  of 
the  animal  to  which  it  belongs ;  its  reaction,  like  that  of  the 
blood,  is  alkaline. 

The  morphological  elements  which  it  contains,  beside  the 
white  globules  and  the  glohuliiies^  similar  to  those  of  the 
blood,  are  the  red  globules^  whose  presence  in  certain  parts 
of  the  lymphatic  system  can  only  be  explained  by  transfor- 
mation of  the  white  lymph  globules  into  red  (see  page  114); 
indeed  we  find  all  the  intermediate  forms  between  these  two 
elements.  Finally,  we  discover,  by  means  of  the  microscope, 
numerous  particles  of  fat  in  suspension  animated  by  the 
molecular  movement  called  the  Brunonian  or  amoeboid  move- 
ment, and  surrounded  by  a  thin  layer  of  albumen  {haptogeiwus 
membrane  of  MuUer),  which  prevents  these  fatty  particles 
from  fusing  with  each  other  and  thus  forming  small  drops. 

The  composition  of  the  fluid  part  of  the  lymph  appears  to 
resemble  closely  that  of  the  liquor  of  the  blood.  It  contains 
fibrine,  but  fibrine  which  does  not  readily  coagulate  of  itself 
{Bradyfibrine  ;  Polli,  Virchow),  and  which  is  here,  as  in  the 
blood,  the  result  of  a  more  or  less  spontaneous  separation  of 
Denis's  plasmine  (Denis  of  Commercy).  —  (See  page  129). 
The  clot,  thus  formed,  is  soft  and  difiiuent :  exposure  to  the 
air  for  some  time  causes  it  to  change  its  color  from  white  to 
pink  or  light  red.  After  the  separation  of  the  fibrine  a  smaller 
quantity  of  albumen  remains  in  the  lymphatic  liquor  than  in 
the  blood  (42  to  1000) ;  but  there  is,  no  doubt,  some  albumen 
concealed  which  is  not  coagulable  by  heat,  especially  some 
forms  of  peptones^  which  we  shall  examine  when  on  the  sub- 
ject of  digestion;  still,  the  quantity  of  albumen  must  be 
always  comparatively  small,  even  in  the  chyliferoiis  ducts ; 
for,  according  to  CI.  Bernard,  these  vessels  absorb  very  few 
albuminoids.  We  reserve  the  question,  however,  and  shall 
return  to  it  in  studying  absorption  and  the  theory  of  the 
peptogens  (of  Schifi*).  In  any  case,  the  comparative  lack  of 
albumen  in  the  lymph  in  general  appears  to  indicate  that,  in 

*  G.  Colin,  "  Traite  de  Physiologio  Comparee  des  Animaux.'* 
2d  edition.     Paris,  18/2,  Vol.  IL,  p.  112. 


198  EPITHELIAL  GLOBULES. 

this  respect,  the  lyiuph  must  be  considered  as  formed  of  that 
part  of  the  liquor  of  the  blood  which  is  not  employed  for  the 
imtrition  of  any  of  the  tissues. 

The  lymph,  in  fact,  contains  excrementitial  products  of 
the  tissues:  it  contains  extractive  matters,  especially  urea 
(Wurtz),  which  is  found  in  larger  proportion  here  than  in  the 
blood.  The  urea  here  appears  as  the  result  of  the  combus- 
tion of  that  quantity  which  we  found  was  wanting  in  the 
liquor  of  the  lymph,  in  comparison  with  the  liquor  of  the 
blood. 

The  other  elements  of  the  lymph  are  less  important :  they 
are  salts,  resembling  those  of  the  serum  of  the  blood  (princi- 
pally chlorides  and  sulphates).  Schmidt  even  discovered 
iron,  in  small  quantities,  in  ashes  of  the  lymph  and  chyle. 

The  lymph,  like  the  blood,  contains  also  gases  and  these 
are  the  same  as  those  found  in  the  blood ;  it  seemed  at  first 
natural  to  suppose  the  proportion  of  oxygen  and  carbonic 
acid  in  the  lymph  to  be  the  same  as  in  the  venous  blood : 
this,  however,  is  not  the  case.  Recent  experiments  by 
Hammarsten  have  proved  that  the  lymph  contains  less  car- 
bonic acid  than  the  venous  blood.  Tliis  fact  appears  unim- 
portant, but  we  shall  see  its  significance  when  treating  of  the 
respiratory  combustion  which  goes  on  in  the  deeper  tissues. 

The  manner  in  which  we  interpret  generally  the  relations 
of  the  origin  of  the  lymphatic  system  to  the  epitheliums  will 
not  apply  to  all :  it  applies  to  the  skin,  the  mucous  coat  of 
the  mouth,  and  the  mucous  membrane  in  general;  but  in  the 
small  intestine  the  lymphatic  network  is  separated  from  the 
epithelium  by  a  blood  network:  we  shall  seek  to  explain 
this  arrangement  later,  in  reference  to  absorption.  The 
mucous  coat  of  some  organs  appears  to  be  entirely  without 
lymphatic  plexus :  as,  for  instance,  that  of  the  uretln-a,  the 
bladder,  the  nasal  fosssB,  the  oesophagus  (?)  ^  In  the  deep 
origins  of  the  lymphatic  vessels  (connective  tissue,  muscles, 

^  The  existence  of  lymphatics  in  the  mucous  coat  of  these  organs 
has  been  the  subject  of  numerous  investigations. 

According  to  "Sappey,  that  of  the  urethra  is  certainly  furnished 
with  lymphatic  vessels:  they  are  very  fine  and  thin,  and  their  small 
branches  converge  in  the  frenum  of  the  penis,  whence  they  pass 
into  the  ganglions  in  the  fold  of  the  groin;  but  they  communicate 
behind  with  the  lymphatic  vessels  of  the  seminiferous  organs  and 
of  the  testicle,  which  explains  the  propagation,  even  to  the  scro- 
tum of  the  hlennorrhacjic  angeioleucitis  (Sappey).  Belajeff  carried 
on  his  minute  researches  as  to  the  structure  of  the  lymphatic  capil- 


■ 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS.    199 

bones),  we  cannot  easily  admit  of  its  existence,  principally 
because  pathological  phenomena  do  not  disclose  these  spaces 
in  the  depths  of  the  organs :  indeed,  the  slightest  injury  to 
the  epitheliums  instantly  affects  the  lymphatic  system  (lym- 
phitis,  adenitis)  ;  while  injury  to  the  deeper  organs,  the 
bones,  for  instance,  gives  rise  to  no  such  complication,  unless 
the  disease  proceed  from  the  deeper  parts  towards  the  sur- 
face. 

Along  the  course  of  the  lymphatic  vessels  are  found  gan- 
glions, whose  complicated  structure  will  be  better  understood 
after  study  of  their  development :  they  are  originally  plexus 
of  lymphatic  capillaries,  ramified,  anastomosed,  and  rolled  up 
into  a  ball ;  the  parenchyma,  thus  formed,  retards  the  flow 
of  the  lymph,  which  crosses  it ;  and  the  white  globules,  which 
are  to  be  poured  into  the  blood,  multiply  at  these  points. 

The  origin  of  the  lymphatic  system  is  another  of  the 
subjects  on  which  physiologists  are  least  agreed.  The  new 
processes  of  investigation,  however,  especially  injection  of 
nitrate  of  silver,  have  enabled  us  to  solve  some  points  of  this 
important  question. 

In  the  first  place,  it  has  been  demonstrated  that,  beside  the 
lymphatic  vessels  subjacent  to  the  tissues,  numerous  spaces 
of  lymphatic  origin  are  found  in  the  deep-seated  tissues,  not 
only  in  the  glands  (which  are  also  derived  from  the  epithe- 

laries  in  the  lymphatic  vessels  of  the  gland  and  of  the  canal  of  the 
urethra. 

The  bladder,  on  the  other  hand,  is  entirely  without  lymphatics. 
Sappey  has  shown  that  the  trunks  in  this  organ,  described  by 
Cruikshanck  and  Mascagni,  do  not  begin  in  it,  but  in  the  prostate 
gland,  and,  in  order  to  reach  the  intra-pelvic  ganglion,  pass  along 
the  postero-lateral  parts  of  the  bladder.  The  non-absorption  of 
the  vesical  mucus  is  sometimes  explained  by  this  absence  of  lym- 
phatics, but  this  is  really  an  essentially  epithelial  phenomenon. 

The  lymphatic  vessels  of  the  pituitary  body  have  long  been  a 
subject  of  dispute  between  anatomists.  In  spite  of  the  descriptions 
of  Cruveilhier,  Sappey  refused  to  admit  of  their  existence,  becanse, 
after  injection  of  the  vessels,  it  was  impossible  to  follow  them  up 
to  their  terminal  ganglions.  Now,  since  the  researches  of  Simon, 
Panas,  and  Sappey,  their  existence  can  no  longer  be  denied,  for 
they  have  been  traced  as  far  as  the  stylo-pharyngeal  ganglions,  up 
to  a  large  ganglion  situated  close  to  the  axis,  which  is  the  highest 
ganglion  in  the  body  (Sappey). 

The  case  is  the  same  with  the  lymphatic  vessels  of  the  oeso- 
phagus, but  those  of  the  palpebral  and  ocular  conjunctiva  are  still 
disputed  (Sappey). 


200  EPITHELIAL  GLOBULES. 

lium),  but  also  in  the  different  kinds  of  connective  tissue, 
which  constitute  the  interstitial  tissue  of  the  various  or- 
gans. 

It  has  been  also  discovered  that  in  several  parts,  even  in 
the  lymphatics  of  the  surfaces,  the  connection  between  the 
original  spaces  and  the  epithelium  is  not  so  close  as  former 
methods  of  investigation  had  led  us  to  suppose :  "in  all  these 
t)arts  examination  of  the  transparent  section  of  the  lymphatic 
vessels,  after  injection  of  nitrate  of  silver,  shows  plainly  that 
they  are  not  absolutely  situated  on  the  surface  of  the  dermis; 
as  injection  of  them,  and  the  exaggerated  distention  caused 
by  the  mercury,  seemed  to  show.  Teichmann  and  Belajeff 
have  proved  that  the  entire  capillary  blood  network  is  always 
placed  above  the  origin  of  the  lymphatics  which,  taken  to- 
gether, also  form  the  upper  network  of  the  integuments." 
(Ch.  Robin.)  Belajeff  meanwhile  notes  that  some  lymphatic 
vessels  of  the  urethral  mucous  membrane  advance  even  to  its 
surface,  so  as  to  touch  the  epithelial  polyhedral  cells  between 
the  papillae,  at  their  base  (!) ;  this  appears  to  be  the  case, 
also,  in  portions  of  the  skin  of  rabbits,  the  dermis  of  which  is 
very  thin. 

At  all  events,  the  perivascular  spaces  of  the  lytnphatic 
vessels  are  closely  connected  with  the  capillary  system  of 
bloodrvessels ;  in  some  parts  the  relation  between  them  is 
still  closer,  and  the  lymphatic  and  blood  capillaries  are  placed 
so  near  each  other  that,  in  a  section  of  one  of  these  meshes, 
we  find  the  lymphatic  space  surrounding  half  or  two-thirds 
of  the  circuDiference  of  the  blood-vessel :  "  the  lymphatic 
space  has  a  genuine  coat  only  on  one  side,  being  bounded 
on  the  others  by  the  blood  capillary  "  (Onimus). 

The  most  signal  instance  of  this  arrangement  is  found  in  the 
perivascular  spaces  which  Ch.  Robin  (1858)  and  His  (18G3) 
have  described  as  existing  around  the  vessels  of  the  enceph- 
alon.  {Lymphatic  sheaths  of  Robin  and  His.)  These  are 
tubes,  with  thin  coats  and  well  defined  hyaline  boundaries, 
surrounding  even  the  finest  capillary  vessels,  in  the  white  and 
gray  matter  of  the  cerebro-spinal  centres,  and  in  the  pia 
mater :  this  sheath  is  not,  however,  found  around  all  these 
vessels.  Their  appearance  and  contents,  which  consist  of  a 
fluid,  containing  several  spherical  nuclei  (globulines)  lead  us 
to  believe  that  these  sheaths  must  belong  to  the  system  of 
lymph  spaces,  "  as  they  would  otherwise  form,  in  addition  to 
the  lymphatic,  arterial,  and  venous  systems,  a  fourth  vascu- 
lar system  whose  terminations   and    nature  would  remain 


GENERAL  PUYSIOLOGY  OF  THE  EPITHELIUMS.    201 

undecided.  But,  before  being  absolutely  sure  that  these  are 
lymphatic  vessels,  we  must  follow  them  from  their  origin, 
which  is  known,  to  the  efferent  trunks  which  they  form  at 
their  junction;  and  decide  the  course  of  these  latter,  up  to 
their  ganglionic  termination,  as  has  been  done  with  the 
other  parts  of  the  lymphatic  system."  (Ch.  Robin.) ^  This 
gap  has  not  yet  been  filled,  and  the  ancient  descriptions  of 
efferent  lymphatic  vessels  of  the  brain  are  scarcely  demon- 
strative :  Fohmann  and  Arnold  made  injections  only  of  the 
sub-arachnoid  cellular  tissue ;  Mascagni  appears  to  have  ob- 
tained more  positive  results  (by  means  of  the  injection  of 
the  arteries  with  the  gelatine,  and  by  tlie  transudation  of  this 
substance),  but  he  could  point  out  neither  the  beginning  nor 
end  of  the  vessels  which  he  has  described.  No  one  has  been 
able  to  discover  these  vessels  since ;  and  their  existence, 
therefore,  seems  very  doubtful  (Sappey). 

The  uncertainty  of  our  knowledge  becomes  still  more 
striking  as  we  approach  the  question  of  the  structure  of  the 
lymphatic  capillaries  which  compose  the  original  network: 
the  most  contradictory  opinions  have  been  expressed  as  to 
the  origin  of  the  lymphatic  vessels  and  their  close  connection 
with  the  surrounding  tissues,  but  we  can  only  review  them 
rapidly. 

1.  The  origins  of  the  lymphatic  vessels  are  formed  l^y  the 
capillary  spaces^  previously  described,  or  by  prolongations 
in  cuUde-sac,  similar  to  the  aforesaid  capillaries,  penetrating 
the  intestinal  villosities  {central  chylifer%  or  chyle-ducts), 
the  papilla3  of  the  tongue,  etc.  This  view,  which  was  that 
of  Mascagni,  Panizza,  and  Cruveilhier,  is  now  corroborated 
principally  by  the  researches  of  Sappey  and  Robin.  The 
coat  of  these  capillaries  is  simply  a  layer  of  epithelial  cells, 
though  some  varicosities  or  other  irregularities  may  be  ob- 
served ;  which,  in  the  thickness  of  certain  organs,  give  them 
a  more  or  less  indented  or  triangular  shape  (and  might  lead 
to  the  belief  that  they  are  connected  by  extremely  fine  links 
to  the  neighboring  elements)  ;  it  is  only  in  the  large  capil- 
laries near  the  efferent  vessels,  that  we  find  in  addition  to 
the  epithelial  layer  (endothelium)  annular  fibres,  and  a  hya^- 
line  membrane  studded  with  nuclei. 

The  lymphatic  capillaries,  like  the  blood  capillaries,  thus 
form  everywhere  a  close  network,  separated  from  the  other 

^  Robin,  article  Lymphatiqnes ;  *'  Dictionnaire  Encyclopediquo 
dea  Sciences  Medicales."     1870. 


202 


EPITHELIAL   GLOBULES. 


anatomical  elements  by  an  epithelial  layer  similar  to  the 
endothelium  of  the  blood-vessels  (Fig.  61) ;  the  continuation 
of  this  layer  shows  that  their  function  consists  essentially  in 
properties  of  simple  endosmosis  or  exosmosis ;  their  proximity 
to  the  blood-vessels,  and  the  sheath  which  in  many  parts  they 
form  for  these  latter  capillaries,  may  show,  perhaps,  that 
their  use  is,  not  only  to  bring  back  to  the  blood  those  fluids 
which  are  the  products  of  destructive  processes,  as  well  as 
those  which  have  not  yet  been  absorbed  by  the  process  of 
nutrition ;  but  also  to  become  filled  with  the  excess  of  the 
plasma  of  the  blood,  which  enters  these  capillaries  at  each 
systole  of  the  ventricle  (E.  Onimus). 

Many  histologists,  however,  assert  that,  before  the  network 
of  the  capillaries  is  formed,  or  at  the  level  of  the  most  super- 
ficial network,  the  origin  of  the  lymphatic  vessels  consists  of 


Fig.  61. - 


■  Vascular  epithelial  cells  (of  the  capillaries)  impregnated  with  nitrato 
of  silver. 


simple  lacunae  partially  lined  with  an  epithelium :  in  this 
icase,  the  real  origin  of  the  lymphatic  vessels  would  consist 
of  the  communications  between  these  lacunae,  either  with  the 
cells  of  the  connective  tissue,  or  with  smaller  lacunae,  the 
network  of  the  interstitial  canaliculi  of  the  connective  tissue. 
This  view  resembles  greatly  an  ancient  theory  (Hunter, 
Haase,  etc.),  according  to  which  hypothesis  these  vessels 
took  their  rise  in  radicles  terminating  in  absorbing  mouths  or 
pores,  in  the  deep  tissues  as  well  as  on  the  surface  of  the 
serous  and  mucous  membranes ;  these  opinions  are  now, 
however,  corroborated  by  experiments  and  histological  re- 


GENERAL  PHYSIOLOGY  OF  THE  EPITnELIUMS.    203 

searches,  which  have  been  nearly  all  undertaken  in  Ger- 
many, and  have  produced  in  some  cases  "such  unlooked- 
for  results  that  we  even  feel  a  sort  of  hesitation  in  relating 
them."i 

2.  The  communication  of  the  lymphatic  radicles  with  the 
corpuscles  of  the  connective  tissue  was  first  pointed  out  by 
Virchow,  who  found,  in  a  hypertrophied  tongue,  lacunae 
unprovided  with  genuine  walls  (lymphatic  capillaries),  and 
containing  prolongations  of  plasmatic  cells,  also  hypertrophied. 
Leydig  and  Heidenhain  have  been  the  principal  advocates 
of  this  theory;  and  the  latter,  in  order  to  explain  the  absorp- 
tion which  takes  place  at  the  point  of  the  intestinal  villosi- 
ties,  supposes  the  existence  of  a  network  of  plasmatic  cells, 
communicating,  on  the  one  hand,  with  the  prolongations  of 
the  epithelial  cells,  and  on  the  other  with  the  central  chyle- 
ducts.  KoUiker  also  embraced  this  opinion,  having  tested  it 
by  experiments  on  the  lymphatic  vessels  of  the  tail  of  a  tad- 
pole, and  Recklinghausen's  view  nearly  resembles  that  of 
these  two  writers :  according  to  him  the  origin  of  the  lym- 
phatic vessels  is  found  in  a  system  of  tubes  which  he  calls 
plasmatic  tubes^  into  some  of  which,  situated  in  the  cornea,  he 
made  injections,  and  which  he  considers  as  special  lacunae 
of  the  connective  tissue.  Now,  according  to  Kolliker,  these 
lacunae  exactly  correspond  to  those  parts  specially  designated 
by  Virchow  under  the  name  of  corpuscles  of  the  connective 
tissue  or  plasmatic  cells;  though  Recklinghausen  persists  in 
considering  them  as  special  lacunae  containing  cellular  ele- 
ments having  no  prolongations  (and  for  which  he  reserves 
the  name  of  corpuscles  of  the  connective  tissue).  However 
this  may  be,  this  view  tends  towards  the  latest  opinion  which 
has  been  enounced  in  reference  to  the  origin  of  the  lymphatic 
vessels. 

3.  The  communication  with  the  lacunce  of  the  connective 
tissue  belongs  partly  to  Recklinghausen's  theory,  but  it  has 
been  chiefly  upheld  by  His,  Tonimsa,  and  Schweigger-Seidel. 
According  to  His,  there  is  direct  communication  between 
the  capillary  vessel  and  the  lacuna,  on  account  of  the  disap- 
pearance of  the  epithelium  of  the  former :  according  to 
Kolliker,  the  lymphatic  capillaries  are  not  intra-cellular  but 
inter-cellular  tubes. 

This  last  opinion  is  the  one  which  appears  destined  to  tri- 

^  H.  Beaunis,  "  Anatomie  Generale  et  Physiologic  du  Systeme 
Lymphatique."     Strasbourg,  Th^se  d'agregation,  18G-3. 


204  EPITUEL1AL   GLOBULES. 

umph :  it  will  be  found  to  resemble  closely  that  of  Reckling- 
hausen if  we  carefully  distinguish,  as  he  does,  what  he  calls  the 
secretion  canals  (lacunaB)  from  the  plasmatic  cells.  In  France, 
this  opinion  has  been  adopted  by  Rouget :  he  considers  the 
lymphatic  vessels  at  their  origin,  in  full  communication  with 
the  vacant  spaces,  the  interstices  of  the  tissues.  Compara- 
tive anatomy  shows  us,  in  the  inferior  animals,  circulations 
which  are  merely  those  in  lacunae  (sipunculi),  and  of  which,  in 
the  superior  animals,  the  only  traces  are  found  in  the  cavernous 
sinus  for  blood,  and  in  the  lymph  spaces  for  the  lymph.  On 
the  other  hand,  the  peritoneum  must  be  considered  as  the  re- 
mains of  what  constitutes,  in  the  inferior  animals,  the  general 
cavity  of  the  body  (between  the  external  integument  and 
the  internal  integument,  or  the  mucous  membrane  used  in 
digestion)  :  now  in  the  superior  animals  the  lymphatic  sys- 
tem still  communicates  freely,  by  small  openings,  with  the 
peritoneal  cavity;  as  was  first  demonstrated  by  Reckling- 
hausen. Having  placed  milk,  or  some  pulverulent  substance 
in  suspension  in  a  fluid,  on  the  diaphragmatic  sui-face  of  the 
peritoneum,  he  found  that  the  drops  of  fat  or  other  granula- 
tions passed  the  epithelial  layer  at  certain  points;  exami- 
nation of  the  peritoneal  serous  membrane,  by  the  aid  of 
nitrate  of  silver,  convinced  him  that  these  points  correspond 
to  special  j^ores^  situated  between  the  cells  of  the  peritoneal 
epithelium  (of  the  phrenic  portion),  and  leading  to  lacunae 
which  form  the  commencement  of  the  lymphatic  vessels  of 
the  diaphragm.  These  ficts  have  been  verified  in  Germany 
by  Ludwig,  Schweigger-Seidel,  Dybrowshy,  Uogiel,  etc. ;  the 
same  experiments  were  successfully  repeated  by  Rouget, 
who  found  that  spontaneous  injection  of  colored  particles 
took  place  in  the  lymphatic  vessels  of  tlie  diaphragm,  when 
these  substances  were  injected  into  the  peritoneal  cavity  of 
the  living  animal ;  Ranvier  also  found  that  they  penetrated 
these  pores,  when  placed  on  the  abdominal  surface  of  the  dia- 
phragm of  an  animal  lately  killed. 

Recent  investigations  by  Ranvier,  however,  seem  to  show 
that  the  orifices  by  means  of  which  this  absorption  is  produced, 
far  from  being  open  when  in  their  natural  state,  open  only  at  the 
moment  when  the  reabsorbed  particles  pass  through.  The 
arrangement  of  these  orifices  is  not  plain,  as  yet:  they  were 
supposed  to  exist  in  all  parts  of  the  peritoneum  (Schweigger- 
Seidel  and  Dogiel),  and  even  in  the  mesentery ;  but,  on 
resuming  the  subject,  Ranvier  became  convinced  that  there 
are  neither  absorbing  mouths  nor  stomata  in  these  parts,  but 


GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS,    205 

really  holes,  by  means  of  which  the  two  sides  of  the  mesen- 
tery are  brought  into  conmiunication  with  each  other. 
These  orifices  appear  to  resemble  in  structure  those  which  he 
has  described  as  belonging  to  similar  parts  of  the  epiploon. 
(For  particulars,  see  Ranvier,  "  Soc.  de  Biologie,"  1872,  and 
H.  Farabeuf,  "De  I'Epiderme  et  des  Epitheliums,"  p.  171.) 

We  may  conclude  from  this  that  the  connective  tissue 
represents  one  of  the  principal  origins  of  the  lymphatic  sys- 
tem, and  that  the  loose  cellular  tissue  may  be  considered  as  a 
vast  lymphatic  chambered  sack,  communicating  directly  with 
the  lymphatic  vessels.  Pathological  anatomy  furnishes 
numerous  proofs  of  this  (Ranvier),  as  well  as  comparative 
anatomy,  and  the  study  of  tlie  development  of  the  lymphatic 
vessels,  and  of  the  tissues  called  lymphoid  tissues  :  thus  the 
boundaries  between  the  sacks  or  lymphatic  reservoirs  of  the 
inferior  vertebrated  animals  and  the  surrounding  connective 
tissue  are  scarcely  marked,  and  Meyer  considers  the  former 
lacunas  of  cellular  tissue  (frogs).  As  we  ascend  the  scale  of 
the  vertebrated  animals,  and  find  that  the  lymphatic  system 
which  exists  in  a  distinct  form  only  in  these  animals,  is  more 
and  more  clearly  developed,  we  see  that  it  arises  from  modi- 
fications of  the  connective  tissue:  Leydig  found  the  adventi- 
tious tunic  of  the  vessels  of  the  mesentery  in  many  bony  fish 
transformed  into  areola?  filled  with  small  colorless  cells,  that 
is,  really,  into  a  genuine  lymphatic  sheath ;  the  same  phe- 
nomenon is  obser\  ed  in  the  adventitious  tunic  of  the  arteries 
of  the  spleen,  the  connective  tissue  of  which  changes  grad- 
ually into  this  lymphoidal  reticulum,  which  constitutes  the 
corpuscles  of  Malj)ighi  and  the  lymphatic  ganglions. 

The  structure  of  the  lymphatic  ganglions  is  the  last  proof 
which  we  shall  mention  of  the  close  connection  between  the 
lymphatic  system  and  the  connective  tissue.  These  gan- 
glions, into  the  histological  study  of  which  we  cannot  now 
enter,  have  been  always  justly  considered  as  formed  by  the 
clustering  of  the  lymphatic  capillaries  (see  page  199) ;  close 
investigation  has  lately  shown  that  they  are  essentially  com- 
posed of  connective  tissue  whose  meshes  are  more  or  less 
free,  and  in  which  (lymphatic  lacuna?)  the  lymphatic  current 
is  difi*used,  drawing  with  it  the  lymph  corpuscles  (page 
198)  which  are  developed  in  it  by  proliferation  of  the  plasmic 
cells,  exactly  as  the  globules  of  pus  are  developed  by  similar 
proliferation  in  any  inflammation  of  the  connective  tissue: 
this  ex])lains  the  resemblance,  or  rather,  the  morphological 
identity,  of  the  pus  globules  and  the  lymph  or  white  globules 
of  the  blood. 


206  EPITHELIAL  GLOBULES. 

We  find  besides  every  transition  between  the  lymphatic 
ganglions  and  the  connective  tissue  properly  so  called :  the 
connective  tissue  of  the  intestinal  mucous,  which  is  formed 
of  loose  trabeculae,  surrounding  spaces  abounding  in  white 
globules,  and  into  which  numerous  lymphatic  capillaricfS 
open  (lacunoB^  lymphatic  sinus),  according  to  His  {adenoid 
tissue)^  represents  the  rudimentary  tissue  of  a  lymphatic 
ganglion  stretched  out  and  diffused;  this  tissue  becomes 
compact  in  places,  taking  more  decided  shapes,  and  forming 
what  are  called  closed  follicles,  either  detached,  or  joined  as 
in  Peyer's  patches;  their  structure  has  long  been  recognized 
as  identical  with  that  of  the  lymphatic  ganglions. 

The  spleen  is  itself  a  lymphatic  ganglion,  though  of  a 
peculiar  kind  ;  it,  too,  is  formed  of  connective  tissue  (sheaths 
of  the  splenic  arteries)  changed  into  adenoid  tissue;  this 
tissue,  however,  is  not  furrowed  by  lacunae  or  lymphatic 
sinus ;  the  blood  here,  is  itself  diffused  through  the  spaces 
in  the  tissue,  drawing  with  it  the  white  globules  which  are 
constantly  being  developed.  The  particulars  of  the  form 
assumed  by  this  tissue  in  order  to  produce  both  the  Malpi- 
ghian  corpuscles,  and  the  substance  oi  the  pulp  of  the  spleen, 
may  be  found  in  treatises  on  histology ;  but,  thanks  to  the 
labors  of  Gray,  Billroth,  Schweigger-Seidel,  and  W.  Miiller, 
in  the  midst  of  all  its  varieties,  the  adenoid  (lymphoid)  con- 
nective tissue  may  always  be  recognized :  it  is  a  collection  of 
lymphatic  ganglions  or  glands,  more  or  less  united  together, 
and  in  which  blood-vessels  take  the  place  of  lymphatic  ducts : 
the  spleen  is,  in  short,  a  lymphatic  sanguineous  gland  (H. 
Frey). 

Thus,  if  the  spleen  be  destroyed  or  taken  away,  we  observe 
general  hypertrophy  of  the  other  lymphatic  glands,  which 
appear  to  prepare  themselves  to  take  the  place  of  the  spleen, 
for  forming  the  white  globules :  this  hypertrophy  of  the  lym- 
phatic ganglions  has  been  observed  in  animals  after  ablation 
of  the  spleen,  and  in  man  after  it  has  become  degenerate  or 
has  been  destroyed  (Fuhrer). 

This  rapid  anatomical  sketch  shows  us  very  plainly  what 
are  the  physiological  functions  of  the  spleen ;  we  shall  study, 
later,  the  indirect  and  not  well  understood  influence  which 
it  exercises  on  the  digestive  functions ;  but  in  the  mean  w^iile 
we  must  look  upon  that,  as  well  as  all  the  lymphatic  glands,  as 
essentially  a  centre  of  formation  for  the  white  globides:  the 
venous  blood  of  the  spleen  is  also  remarkably  rich  in  lymph 
globules;  while  the  arterial  blood  which  enters  it  contains 


'GENERAL  PHYSIOLOGY  OF  THE  EPITHELIUMS.   207 

one  for  every  two  hundred  and  twenty  red  globules,  the  venous 
blood  which  flows  out  contains  one  to  sixty  (His)  and  even 
one  to  five  or  four.  (Vierordt,  Funke.)  The  influence  which 
'the  spleen  exercises  in  relation  to  the  red  globules  is  still  so 
far  from  being  decided,  that  some  maintain  that  it  is  a  seat 
of  destruction  of  these  elements  (Beclard,  Kolliker),  while, 
according  to  others,  it  is  a  laboratory  for  their  prodnctiou 
(Funke,  J.  Bennett). 

The  following  facts  are  adduced  as  proofs  of  its  destructive 
function  of  the  red  globules:  an  animal  in  which  ablation 
of  the  spleen  has  been  accomplished,  exists  longer  without 
food  than  one  which  is  sound :  its  blood  does  not  change  as 
quickly  into  red  globules ;  the  lymph  which  comes  from  the 
spleen  (for  this  organ  also  contains  lymphatic  vessels)  is 
generally  tinged  with  red.  Some  observers  have  remarked 
a  sort  of  plethora  (or  hyperglobulia)  in  animals  whose  spleen 
has  been  removed ;  but  these  observations  do  not  agree  with 
the  results  furnished  by  clinical  surgery. 

The  red  globules  are  evidently  destroyed  in  the  spleen,  as 
in  any  organ  or  tissue  in  which  active  transformation  takes 
place ;  this  may  be  readily  observed  in  pathological  cases,  in 
which  we  find  a  large  quantity  of  remains  of  the  coloring 
matter  of  the  red  globules  {paludal  cachexia) :  but  it  is 
still  more  likely  that  a  large  number  of  red  globules  are 
formed  in  the  spleen,  in  the  physiological  condition,  in  the 
sense  that  the  white  globules  which  were  produced  in  it,  are 
beginning  to  change  into  colored  blood  corpuscles :  indeed, 
an  abundance  of  globules,  in  an  intermediate  state  between 
the  white  and  the  red,  are  found  in  the  splenic  veins,  as 
also  red  globules,  possessing  all  the  features  which  distin- 
guish young  elements  (small  size,  less  flattened  shape,  greater 
resistance  to  the  action  of  water,  etc.). 

There  are  also  some  glandular  organs,  resembling,  no  doubt, 
nearly  the  class  of  lymphatic  ganglions  and  spleen ;  such  as 
the  thyroid  gland,  the  thymus,  and,  perhaps,  the  supra-renal 
capsules;  but  our  anatomical  ideas  on  these  subjects  are  not 
yet  sufiiciently  precise,  and  our  physiological  theories  are  too 
hypothetical,  to  allow  us  to  attempt  profitably  the  study  of 
these  so-called  vascular  blood  glands. 


PART    SIXTH. 
DIGESTIVE    SYSTEM. 

I.   Object  of  Digestion.  —  Inanition.  —  Food. 

The  aim  of  the  digestive  functions  is  to  transform  the 
Bubstances  borrowed  from  without,  so  us  to  enable  them  to 
pass  into  the  system,  to  be  absorbed  and  carried  into  the 
current  of  the  circulation,  in  order  to  renew  the  organs,  and 
keep  up  their  functions. 

These  reconstructive  substances  are  food. 

By  privation  of  food,  animals  are  re<luced  to  a  state  of 
inanition:  the  inevitable  consequences  of  prolonged  inani- 
tion are  gradual  loss  of  weight,  cold,  and  death ;  animals  die 
when  they  have  lost  -^^  of  their  original  weight  (Chossat.)^ 

This  loss  of  weight  is  produced  sooner  in  some  animals 
than  in  others :  cold-blooded  animals  will  endure  privation 
of  food  thirty  times  longer  than  the  warm-blooded,  and  some- 
times, even,  for  an  almost  incredible  space  of  time :  thus  CI. 
Bernard  has  known  frogs  go  entiiely  without  food  for  nearly 
three  years,  while  a  small  biid  dies  of  hunger  after  two  or 
three  days. 

Inanition,  as  observed  in  persons  subjected  to  a  stiict  diet, 
not  only  affects  the  general  temperature,  but  also  the  daily 
variations  in  temperature :  even  when  there  is  no  fever,  this 
may  vary  S**.  This  fact  should  be  taken  into  account,  in  esti- 
mating the  temperature  of  persons  suffering  from  intermittent 
fever,  who  have  long  been  on  a  low  diet. 

Some  of  the  alimentary  substances,  intended  to  repair  the 
incessant  waste  of  the  system,  are  immediately  absorbed  ; 
while  others,  which    are   deposited   on   the   surface   of  the 

*  Chossat,  "Rech arches  Experimeutakssurrinanition."  Paris, 
1843,  in  4to. 


OBJECT  OF  DIGESTION.  209 

digestive  orgniis,  must  first  undergo  a  change,  from  being 
subjected  to  the  influence  of  the  juices  of  these  organs.  This 
is  because  the  food,  received  into  the  mouth,  traverses  the 
different  parts  of  the  digestive  canal  successively,  and  is  sub- 
jected in  its  course  to  various  mechanical  influences,  espe- 
cially that  of  the  different  fluids  which  serve  to  liquefy  and 
transform  it.  These  modifications  are  not  generally  very 
striking ;  they  appear  to  affect  only  the  state  of  cohesion  of 
the  substances ;  insoluble  elements  being  rendered  soluble, 
and  coagulable  elements  incoagulable,  etc.,  while  the  im- 
changed  parts  are  thrown  off. 

No  aliment  is  complete,  unless  it  contains  all  the  elements 
of  which  the  tissues  of  the  body  are  composed. 

1.  Beside  their  organic  principles  the  animal  and  vegetable 
matters  which  we  consume  contain  various  mineral  products: 
such  are  the  alkaline  or  alkaline-earthy  salts,  sulphur,  phos- 
phorus, iron,  all  elements  necessary  to  every  cell  of  our 
organs.  Iron  is  administered  to  a  chlorotic  person  as  food, 
because  iron,  which  is  one  of  the  indispensable  elements  of  the 
economy,  has  been  diminished  in  the  blood.  These  mineral 
substances  alone,  are  incapable  of  supporting  life ;  and  if 
those  which  are  borrowed  from  the  organic  kingdom  are 
found  sufficient  for  this  purpose,  it  is  only  because  they  con- 
tain in  themselves  a  certain  proportion  of  mineral  matters. 

The  mineral  salt  that  appears  most  indispensable  to  nour- 
ishment is  chloride  of  sodium.  Daily  experience  proved 
long  ago  that  man  cannot  do  without  this  salt,  and  the  reli- 
gious corporations  which  sought  to  subject  themselves  to  the 
severest  privations,  tried  in  vain  to  banish  chloride  of  sodium 
from  their  food.  Physiological  experiments  on  animals  show 
(AYundt,  Rosenthal,  Schultzen)  that  this  salt  is  indispensable 
to  the  system^  and  serious  consequences  have  followed  its 
suppression.  Physiological  chemistry  explains  these  facts  by 
si  lowing  that  chloride  of  sodium  enters  into  the  composition 
of  nearly  every  part  of  the  organism,  and  is  especially  indis- 
pensable to  the  constitution  of  the  blood  serum  and  carti- 
lages. It  appears  to  assist  in  the  process  of  the  nutrition  of 
the  tissues,  and  is  indispensable  to  the  formation  of  the  bile, 
pancreatic  and  gastric  juices.  Cattle-breeders  are  well 
acquainted  with  the  favorable  influence  produced  on  the 
development  of  animals  by  administration  of  chloride  of 
sodium;  without  asserting  tjiat  mixture  of  this  salt  with  the 
food  produces  increase  of  growth  and  fat^  we  must  admit 
(Boussingault)    that   animals   fed   in   this   w^ay   have   more 

14 


210  DIGESTIVE  SYSTEM. 

glossy  and  thicker  hair,  a  more  healthy  appearance,  are  more 
sprightly  and  active,  etc. 

Attempts  have  been  made,  but  without  success,  to  substi- 
tute chloride  of  potassium  for  the  sodium  salt ;  it  has  been 
found,  however,  instead  of  possessing  the  useful  properties 
of  the  latter,  to  produce  serious  injury.^ 

2.  The  principal  aliments  are  those  furnished  by  the  animal 
kingdom,  that  is  the  different  forms  of  albumen,  designated 
under  the  common  name  of  proteine  substances^  and  several 
other  similar  elements  classed  together  under  the  name  of 
caseines.  All  these  substances  contain  Oxygen  (O),  Hydro- 
gen (H),  Carbon  (C),  and  Nitrogen  (N),  besides  a  certain 
quantity  of  Sulphur  (S)  and  Phosphorus  (P),  mineral  salts, 
etc.  They  also  contain,  probably,  iron  in  small  quantities, 
though  this  is  not  yet  proved  in  all  cases. 

Some  vegetable  products  supply  the  same  aliment,  such 
as  gluten  or.  vegetable  jibrine^  which  is  found  in  many  seeds, 
particularly  cereals ;  vegetable  albumen.,  found  in  emulsive 
seeds  and  vegetable  juices,  and  legumine  or  vegetable  caseine, 
found  in  large  quantities  in  the  seeds  of  leguminous  plants. 
These  substances  may  all  be  classed  under  the  name  of 
albuminoids.  The  transformations  undergone  by  the  albu- 
minoid substances  contained  in  plants  bear  a  striking  resem- 
blance to  those  which  take  place  in  the  animal  economy,  and 
which  we  shall  proceed  to  examine.  During  the  germina- 
tion of  seeds,  the  albuminoid  substances  contained  in  plants 
give  rise  to  digestive  ferments  bearing  the  essential  features 
of  some  of  the  ferments  furnished  by  the  animal  organs. 
Thus  the  diastase  produced  by  the  germination  of  cereals, 
closely  resembles  the  ferment  which  we  shall  see  is  found  in 
the  saliva  and  in  the  pancreatic  juice. 

3.  Next  come  the  ternary,  non-nitrogenous  (or  non-azotized) 
principles  containing  (C),  (H),  and  (O),  in  the  proportions  re- 
quired for  the  formation  of  sugar,  starch,  dextrine,  gum,  and 
various  mucilages ;  all  of  these  substances  are  incapable  of 
directly  forming  globules,  the  prevailing  matter  of  which  is 
nitrogen.  These  substances  are  derived  chiefly  from  the  veg- 
etable kingdom ;  they  are  also  found  in  animal  food,  but  in  very 
small  quantities.  Sugar  is  found  in  milk,  in  the  liver,  and  in 
the  blood  which  flows  from  this  organ ;  it  has  been  discovered 

1  See  CI.  Champy,  "  fitude  comparee  de  1' Action  Physiologique 
des  Sels  Potassiques  et  Sodiques  et  de  leurs  Chlorures."  These  de 
Strasbourg,  IS/'O,  No.  290. 


i 


FOOD.  211 

in  many  epitheliums :  in  that  of  the  cerebral  ventricles  are 
found  white  granules,  some  of  which,  in  their  behavior 
witli  the  reagents,  resemble  amylaceous  matter,  and  others 
dextrine ;  sugar  also  exists  in  the  muscles  and  accumulates 
when  they  are  not  in  action  (as  after  long  repose ;  after 
section  of  the  motor  nerves,  and  in  the  muscles  of  the  foetus), 
(Rouget).  The  integument  of  the  non-vertebrated  animals 
is  formed  of  a  glycogenous  substance :  this  is  the  chitine  of 
insects,  the  tunicine  of  the  tunicata  {animal  cellulose)^  (Carl 
Schmidt).  These  substances  are  transformed  into  sugar  by 
boiling  with  potash  (Berthelot,  Rouget).  All  therse  classes 
of  alimentary  substances  become  capable  of  being  absorbed 
by  contact  with  the  digestive  organs. 

4.  The  last  class  of  alimentary  substances  is  the  fats ; 
these  do  not  require  to  be  digested,  in  the  proper  sense  of 
the  word;  that  is  to  say,  the  digestive  juices  produce  no 
change  in  them ;  the  fats  are  unchanged.  They  may,  even, 
be  absorbed  by  other  surfaces  than  those  of  the  digestive 
organs,  as  by  the  skin,  for  instance ;  we  know  that  if  fatty 
substances  be  rubbed  on  the  skin,  they  will  penetrate  the 
epidermis :  this  is  the  only  possible  mode  of  nutrition  by 
means  of  the  external  integument.  The  fatty  substances  are 
found  in  both  the  animal  and  vegetable  kingdom. 

Thus  we  see  that  nourishment  may  be  derived,  almost 
indifferently,  from  either  the  animal  or  vegetable  kingdom : 
the  amylaceous,  glycogenous  matters,  forming  almost  the 
essential  element  of  vegetables,  are  also  found  in  animal 
products;  thus  we  know  that  some  savage  tribes  make  fer- 
mented liquors  (alcohol)  with  the  sugar  found  in  mares' 
milk.  We  have  an  instance,  on  the  other  hand,  of  an  aliment 
which  is  apparently  and  essentially  animal,  though  found 
in  the  vegetable  kingdom :  in  the  cheese  which  the  Cliinese 
make  from  legumine  {caseine)  derived  from  the  fruit  of  legu- 
minous plants. 

It  is  especially  important,  however,  to  remark  that  the 
property  of  forming  some  of  these  substances  does  not  belong 
to  vegetables  only,  to  the  exclusion  of  animals :  the  forma- 
tion of  albuminoid  substances  evidently  belongs  to  both 
kingdoms;  the  discovery  of  animal  glycogeny  (C.  Bernard) 
proves  that  animals,  as  well  as  vegetables,  can  and  do  nat- 
urally form  amylaceous  substances,  and  the  same  is  true 
with  regard  to  fatty  substances :  we  owe  to  experiments  by 
F.  Huber,  Milne-Edwards,  and  Dumas,  the  knowledge  of  the 
fact   that   bees,  fed   exclusively  on  sugar,  still   possess  tJie 


212  DIGESTIVE  SYSTEM. 

property  of  forming  wax,  which  is  a  fatty  substance.  The 
possibility  of  an  animal  organism  making  any  fatty  substance 
used  to  be  denied  by  many  chemists  and  physiologists. 

The  ammal  and  vegetable  kingdoms  also  contain  sub- 
Btances  which  resist  the  action  of  the  digestive  juices,  and 
consequently  pass  through  the  intestinal  canal  only  to  reap- 
pear in  the  excrementitious  products,  separated  from  the 
alimentary  principles  accompanying  them.  These  are,  on 
the  one  hand,  elastic  and  connective  tissue,  the  digestion  of 
which  is  very  difficult  and  even  impossible  to  some  persons ; 
and,  on  the  other,  numerous  vegetable  elements  the  most 
common  form  of  which  is  the  cellular  or  ligneous,  forming 
the  skeleton  of  most  vegetables,  the  envelope  of  certain 
seeds,  etc. 

There  is,  finally,  a  peculiar  class  of  substances,  which  must 
be  considered  as  aliments,  though  they  undergo  little  or  no 
change  in  passing  through  the  system  and  the  interior  of 
the  tissues ;  they  appear  to  produce  the  effect  of  diminishing 
combustion,  or  rather  of  rendering  it  more  efficacious :  in 
short,  they  promote  the  transformation  of  heat  into  force, 
and  render  the  true  alimentary  substances  previously  in- 
gested, more  useful.  Whence  the  name  of  reserve  or  eco- 
nomical aliments,  bearers  of  force  (dynamophorous).  This 
singular  class  of  substances  which  are  not  alimentary,  and 
yet  are  aids  to  alimentation,  has  been  the  subject  of  numerous 
investigations,  showing  their  number  and  the  mode  of  action 
peculiar  to  each.  Alcohol  stands  at  the  head  of  this  class : 
according  to  many  physiologists  alcohol  is  burned  in  the  sys- 
tem, serving  thus  to  produce  heat  immediately  (Liebig,  Hepp, 
Hirtz,  Schulinus) ;  but  recent  investigations  of  Lallemand  and 
Perrin  show  that  if  alcohol  be  received  into  the  system  it  merely 
passes  through  it,  and  is  always  found  again,  as  in  the  blood 
and  tissues,  especially  the  nervous  tissue,  in  which  it  appears 
to  take  up  its  abode  for  some  time :  in  short,  it  is  not  con- 
sumed, and  its  presence  as  an  alimentary  substitute  only 
serves,  by  economizing  combustion,  to  increase  its  utility. 
We  can  understand  thus,  that  alcoholic  drinks  may  be  indis- 
pensable, in  some  degree,  to  a  man  who  is  obliged  to  perform 
severe  labor,  with  insufficient  nourishment ;  as  to  the  fatal 
excess  which  so  often  succeeds  a  moderate  use  of  these 
drinks,  physiology  shows  us  that  our  efforts  should  be  directed 
less  against  this,  than  against  the  conditions  which  make  the 
use  of  alcohol  an  imperious  and  fatal  necessity  for  the  work- 
ing-man (Moleschott). 


FOOD.  213 

After  alcohol  come  the  active  principles  of  tea,  coffee,  and 
similar  drinks:  theine,  cafeine,  theobromine,  coumarine 
(tonka  bean),  the  principle  of  Peruvian  coca}  This  latter 
substance  appears  to  affect  the  muscular  system  especially, 
while  the  former  have  more  influence  on  the  nervous  sys- 
tem. Messengers,  travellers,  and  workmen  have  found  that 
by  chewing  the  leaves  of  the  erythroxylum  coca  they 
could  dispense  with  any  solid  or  liquid  food  for  one  or  two 
days :  these  leaves  allay  hunger  and  thirst,  and  sustain  the 
strength.  This  is  the  reason  that  the  Peruvians  deified  this 
tree,  leaves  of  which  were  afterwards  employed  by  the  Incas  for 
money.  Ch.  Gazeau,'^  however,  maintains  that  this  so-called 
power  of  fasting  is  only  ana3sthesia  of  the  stomach  and  oeso- 
phagus, and  that  the  person  is  autophagus^  and  in  a  state  of 
inanition  without  being  aware  of  it.  But  as  hunger  is  a 
universal  sensation  of  the  system,  it  is  scarcely  possible  to 
maintain  this  theory,  in  the  face  of  the  well-known  instances 
of  nutrition  being  kept  up  by  coca  as  well  as  by  alcohol. 
The  action  of  these  latter  substances  cannot  be  explained  by 
referring  it  to  the  presence  of  nitrogen  in  their  composition  and 
regarding  them  as  azotizing  aliments,  the  plastic  aliments  of 
Liebig.  Cafeine,  theine,  etc.,  contain  a  large  quantity  of  nitro- 
gen, but  their  compo^^iliou  closely  resembles  that  of  the  uric 
acid,  XMUthine  and  hypoxanthine,  all  of  which  are  excrementi- 
tious  products  or  waste  from  the  organism :  it  thus  appears  that 
theine,  cafeine,  etc.,  merely  pass  through  the  organism,  and  re- 
appear ill  tlie  excreta,  and  tiiis  has  been  proved  by  experiment. 

Liebig's  extract  of  meat  must  also  be  classed  among  the  eco- 
nomical aliments  {aliments  (T epargne)^  if,  indeed,  this  product 
can  be  said  to  have  any  alimentary  utility  at  all.  This  extract 
is  now  shown  to  be  in  no  way  nutritive.  The  nitrogenous 
crystallizable  princij^les  which  it  contains  are  no  more  nutritive 
than  theine  or  cafeine,  etc. ;  the  only  use  of  this  extract  is  that 
of  a  slight  stimulant  from  the  salts  which  it  contains  (nearly 
one-fifth  of  its  weight).  In  short,  Hepp  and  Miiller's  experi- 
ments (These  de  Paris,  1871)  on  animals,  seem  not  only  to 
Bhow  the  uselessness  of  this  extract  as  an  article  of  food,  but 
also  to  ascribe  to  it  a  poisonous  effect,  when  taken  in  large 

*  Ch.  Marvaud,  "  Etude  de  Physiol ogie  Therapeutique,  Ejffets 
Physiologiques,  et  Therapeutiques  des  Aliments  d'Epargne  ou 
Antideperditeurs.     Alcool,  Cafe,  The,  Coca,  etc."     Paris,  1871. 

*  Ch.  Gazeau,  "  Nouvelles  Recherches  ExpcrimentaleS  sur  la 
Pharmacologie,  la  Physiologie,  et  la  Therapeutique  de  la  Coca." 

hese  de  doctorat,  Paris,  1870. 


i 


214  DIGESTIVE  SYSTEM, 

quantities  :  according  to  Kemraerich  the  exclusive  use  of  the 
extract  of  meat  would  kill  sooner  than  starvation. 

In  studying  the  different  phases  of  the  act  of  digestion,  we 
will  take,  first,  those  which  are  observed  in  the  sub-diaphrag- 
matic part  of  the  canal ;  next,  those  of  the  cavity  of  the 
stomach ;  and,  finally,  phenomena  which  take  place  in  the  pas- 
sage through  the  intestinal  tube  (large  and  small  intestine). 

11.    First  Part  of  the  Act  of  Digestion. 

The  aliments  introduced  into  the  cavity  of  the  mouth  are 
divided  by  the  teeth  {masticati07i),  moistened  and  modified 
by  the  saliva  (salivation),  and  then  carried  into  the  pharynx, 
seized  by  it,  and  pushed  into  the  stomach  by  the  oesophagus 
(deglutitio)i). 

A.  Mastication. 

The  purpose  of  mastication  is  to  divide  the  solid  aliments 
so  that  they  may  be  more  easily  attacked  by  the  digestive 
fluids  of  the  mouth  and  other  parts  of  the  intestinal  canal. 
Meat  and  nitrogenous  substances  are  more  easily  digested  in 
the  stomach  after  they  have  undergone  mastication  in  the 
mouth,  but  the  operation  need  not  be  carried  very  far  in  the 
case  of  aliments  of  this  kind  :  thus  we  observe  that  the  exclu- 
sively carnivorous  animals  have  no  teeth  properly  so  called, 
but  merely  hooks,  with  which  they  tear  their  food  into  large 
pieces.  Mastication  is  indispensable,  on  the  contrary,  in  the 
case  of  aliments  belonging  to  the  vegetable  kingdom ;  the 
greater  number  of  nutritive  vegetable  matters  are  enclosed 
in  a  casing  which  generally  resists  the  action  of  the  digestive 
juices:  the  masticating  system  serves  to  tear  the  cells,  the 
envelope  of  seeds,  etc. ;  prima  digestio  fit  in  ore,  said  the 
ancients :  in  saying  this,  they  spoke  only  of  mastication, 
being  ignorant  of  the  chemical  process  which  takes  place 
durifig  salivation. 

The  lower  jaw,  as  it  rises  and  falls,  represents  a  lever, 
moving  round  a  supposed  axis,  which,  in  movements  of  slight 
extent,  is  centred  in  the  condyles;  but  when  the  mouth 
is  wide  open,  the  separation  of  the  jaws  is  greater,  and  the 
condyles  quit  the  glenoid  cavities,  and  come  further  for- 
ward. The  movement  then  takes  |)lace  round  an  axis  cross- 
ing the  two  upright  branches  of  the  inferior  maxillary  at  the 
level  of  the  ^QuidX  foramen  ;  however  little  the  buccal  cavity 
may  be  opened,  and  even  in  ordinary  mastication,  the  two 


i 


MASTICATION.  215 

movements  are  combined,  as  may  be  proved  by  placing  the 
finger  on  the  temporo-maxillary  articuhition  :  the  rotation 
of  the  condyle  in  the  cavity,  and  its  forward  projection  take 
place  at  the  same  time ;  so  that  it  is  difficult  and  even  im- 
possible to  decide  exactly  on  a  fixed  axis  around  which  all 
the  movements  of  the  jaw  are  made. 

In  all  cases  the  lower  jaw  acts  as  a  lever  of  which  the 
fixed  point  is  behind,  in  the  upright  branch  of  the  bone;  the 
j>oint  of  application  of  the  power,  which  is  represented  prin- 
cii)ally  by  the  masseter  and  temporal  muscles,  is  in  the  front 
edge  of  this  upright  branch ;  the  resistance  may  be  found  in 
diiferent  points:  if  an  aliment  is  to  be  divided,  the  resistance 
lies  on  the  level  of  the  incisors,  and  in  this  case  the  lever 
belongs  to  the  third  kind,  and  the  arm  of  the  power  is  very 
short  in  comj)arison  with  the  arm  of  resistance  (see  p.  103, 
meclianism  of  tlie  muscles).  When  the  food  requires  to  be 
ground,  the  resistance  is  applied  at  the  level  of  the  molars, 
and  its  lever  arm  becomes  shorter,  thus  giving  the  advantage 
to  the  action  of  the  power,  the  lever  arm  of  which  keeps  its 
original  length.  Even  in  the  case  of  a  resistance  opposed  to 
these  latter  molars,  the  fibres  of  the  masseter  may  be  found 
anterior  to  the  resistance ;  and  the  maxillary  lever  then  be- 
comes a  lever  of  the  second  kind,  that  which  is  most  favor- 
able to  the  action  of  the  power  (interresisting  lever^  page 
102). 

There  is  also  a  side  movement  in  the  lower  jaw,  which  is 
restricted  in  man,  but  of  great  extent  in  the  ruminants. 
It  is  due  to  the  contraction  of  the  external  pterygoid 
muscle  which,  by  drawing  one  of  the  condyles  forward, 
brings  it  out  of  the  glenoid  cavity,  while  the  jaw  pivots  on 
the  other  condyle. 

We  see  thus,  that  in  man  mastication  is  a  compound, 
action,  resembling  both  that  of  the  carnivora  and  the 
herbivora  (ruminants),  on  account  of  the  compound  nature 
of  his  food :  the  carnivora,  which  only  tear  their  prey,  make 
no  upward  and  downward  or  sideway  movement ;  thus 
their  condyle  turns  only  on  its  transverse  axis.  In  the 
ruminants  the  sideway  movements  are  very  decided,  and  for 
this  purpose  the  condyle  is  flat  and  movable  in  all  directions. 
Another  type  of  condyle  is  that  of  the  rodents.^  the  antero- 
posterior diameter  of  which  is  of  great  extent,  a  glenoid 
cavity  being  hollowed  out  in  the  same  direction.  In  man, 
the  form  of  the  condyle  is  intermediate  between  all  these, 
while   the   masticatory   movements   are    more   varied,   and 


216  DIGESTIVE  SYSTEM. 

are  combined  in  a  more  comi^lex  manner  than  in  any  other 
animal. 

Beside  the  action  of  the  jaws  in  tearing,  cutting,  and 
crushing  the  food,  there  is  also  an  action  of  the  tongue^  llps^ 
and  cheeks.,  which  aid  mastication  by  pushing  the  food  be- 
tween tlie  teeth,  and  keeping  it  in  place. 

Mastication  is  a  voluntary  act,  and  yet  it  may  be  said  to 
belong,  in  some  respects,  to  the  class  of  reflex  actions :  thus 
mastication  becomes  slow,  difficult,  and  even  impossible, 
when  there  is  an  insufficiency  of  saliva,  or  when  the  want  of 
food  is  not  felt.  There  must,  then,  be  here  as  everywhere,  a 
special  peripheral  impression,  which,  being  reflected  in  the 
nervous  centres  (the  bulb,  in  mastication),  causes  the  phe- 
nomenon of  reflex  action.  Mastication,  like  walking  and 
many  other  movements  which  are,  aj^parently,  quite  volun- 
taiy,  is  performed,  in  a  great  measure,  and  during  most  of 
the  time,  by  means  of  the  mechanism  of  reflex  actions.  (See 
page  45,  Fhysiology  of  the  nervous  centres  :  bulb.) 

B.  Salivation. 

The  organs  of  salivation  are  not  only  the  salivary  glands 
properly  so  called,  but  the  whole  glandular  system  spread 
throughout  the  cavity  of  the  mouth:  such  as  the  molar 
glands,  or  glands  of  the  cheeks,  the  glands  of  the  lips, 
those  of  the  under  surface  of  the  tongue,  those  of  the  roof  of 
the  mouth,  and  those  of  the  velum  of  the  palate,  which  are 
improperly  called  mucous  glands.  All  these  glands  are 
formed  by  masses  of  globules  arranged  in  ramified  tid)es,  open- 
ing, sometimes,  singly  to  the  outside,  and,  at  others,  uniting 
in  a  single  excretory  tube,  Steno's  duct  (parotid),  WhartotHs 
duct  (sub-maxillary).  The  saUva  is  a  deliquium,  produced 
by  the  fusion  of  the  globules  of  these  glands  as  they  fall  into 
decay. 

The  salivary  juice  is  found  to  difier  slightly  in  the  diff*erent 
glands,  but  it  has  one  general  feature,  that  of  being  very 
watery,  and,  in  this  respect,  differs  greatly  from  the  nuicus ; 
it  ifl  water,  containing  scarcely  from  one  to  two  per  cent  of 
solid  matter;  its  reaction  is  alJmliue :  when  taken  from  a 
person  in  a  fasting  condition,  it  is  sometimes  found  to  be 
slightly  acid,  but  this  acidity  is  simply  owing  to  decomposi- 
tion of  the  food  remaining  between  the  teeth. 

The  saliva  contains  an  organic  nitrogenized  (azotic)  sub- 
stance (discovered  by  Leuchs,  1831)  ;  it  is  not  well-defined, 
but  is  a  pecuUar  form  of  albuminous  substance  called  ptya- 


SALIVATION.  217 

line  (Berzelius)  or  animal  diastase  (Mialhe),  resembling 
closely  the  principle  of  sprouting  barley.  This  substance 
has  the  property  of  changing  starch  into  glucose.  The 
parotid  saliva  alone  has  no  power  to  change  starch  into 
sugar  (in  the  horse,  and  in  man)  ;  the  case  is  the  same  with 
the  sub-raaxillary  gland  (the  dog) :  the  power  of  turning 
substances  into  sugar  thus  appears  to  belong  to  the  complex 
product  of  the  diflferent  salivary  glands  and  of  those  glands, 
called  mucous,  which  are  so  abundant  in  the  buccal  cavity. 
This  property  does  not  appear  to  belong  exclusively  to  the 
saliva:  it  is  found  in  nearly  all  animal  substances;  the  mu- 
cous of  the  bladder,  the  blood,  and  the  muscular  flesh  all 
have  it  though  in  a  low  degree. 

The  saccharizing  property  of  the  saliva  is  not  equally 
prominent  in  all  animals :  man  is  one  of  the  most  favored  in 
this  respect,  but  less  so  than  some  of  the  herbivora,  especially 
the  guinea-pig ;  the  saliva  of  the  dog,  so  often  made  use  of 
for  experiments,  is  not  well  adapted  for  this  purpose,  possess- 
ing the  property,  as  it  does,  in  a  much  lower  degree  than 
many  others.  In  man,  this  property  is  developed  only 
with  the  first  appearance  of  the  teeth  (Bidder).  The  ptya- 
line  of  the  saliva  can  only  be  extracted  by  precipitating  it  by 
alcohol,  and  then  redissolving  it  in  water  (general  process 
of  separation  of  the  albuminoid  ferments).  In  all  salivary 
ptyaline  are  found  peculiar  elements  of  a  globular  form, 
called  by  some  authors  pyoid  globules,  and  closely  resem- 
bling the  white  globules.  Leeuwenhoek  had  already  dis- 
covered these  globular  elements,  which  exhibit  decided 
phenomena  of  amoeboid  movements,  and  are  reproduced  by 
means  of  fission  ;  these  inferior  organisms  may  be  compared 
to  ferments,  and  have  a  more  or  less  direct  part  in  producing 
the  chemical  activity  of  the  saliva ;  indeed  we  notice  that 
the  more  abundant  these  organisms  are,  the  greater  is  the 
saccharizing  property  of  the  saliva;  thus,  in  salivation 
(ptyalism)  produced  by  the  use  of  mercury,  Leeuwenhoek's 
corpuscles  are  extremely  numerous,  and  the  saliva  has  the 
property  of  changing  starch  into  sugar  in  the  highest  degree 
(Rouget). 

Ptyaline  is  a  soluble  ferment ;  it  partakes  of  the  nature 
of  an  albuminoid,  but  differs  a  little  from  other  albuminoids 
in  not  being  precipitated  by  a  heat  of  60'^  (C) ;  this  does 
not,  however,  imply  that  it  is  not  destroyed  by  an  increase 
of  temperature  (Frerichs,  Cohnheim),  but  the  temperature 
must  be  raised  at  least  to  the  boiling  point  in  order  to  effect 


218  DIGESTIVE   SYSTEM. 

this  (SchifF) ;  Cohnheim  has  attempted  in  vain  to  prove  that 
ptyaline  is  not  an  albuminoid  substance.^ 

The  other  elements  of  the  saliva  are  salts,  identical  with 
those  of  the  blood,  and  also  sidphocyanide  of  potassium. 
The  existence  of  this  salt,  first  discovered  by  Treviranus,  has 
since  been  the  subject  of  much  dispute:  the  reaction  by 
which  it  is  distinguished  (red  color  produced  by  salts  of 
iron)  has  been  attributed  to  acetates ;  but  distillation  of  the 
saUva  proves  that  it  contains  no  acetic  acid.  It  was  then 
supposed  that  the  sulphocyanide  was  the  result  of  decomposi- 
tion or  was  produced  only  in  pathological  cases  (hydrophobia 
in  dogs)  or  under  the  influence  of  certain  jiervous  or  moral 
conditions  (Eberle).  But  closer  investigation  of  the  subject 
by  Longet,  (Ehl,  Sertoli,  and  Schifi^  has  shown  that  sulpho- 
cyanide is  an  element  which  is  always  present  in  human 
saliva,  though  its  use  is  not  yet  understood. 

The  secretion  of  the  saliva  offers  a  good  example  of  the 
influence  exercised  by  the  innervation  of  the  secretions. 
This  secretion  indeed  is  not  the  result  of  irritation  directly 
produced  by  the  food ;  the  large  salivary  glands  are  too  remote 
from  the  buccal  mucous.  A  reflex  phenomenon  takes  place 
here.  The  peripheral  impression  produced  by  the  food  is 
transmitted  by  a  special  nervous  organ  to  a  reflecting  centre, 
whence  it  is  communicated  to  another  organ  (centrifugal 
nerve)  which  determines  the  secretion.  This  reflecting 
centre  is  not,  as  was  long  supposed,  situated  in  the  ganglions 
of  the  great  sympathetic  nerve:  numerous  experiments  have 
proved  that  it  is  in  the  spinal  cord.^  The  centripetal  nerves 
beginning  in  the  mucous  membrane,  go  to  the  bulb:  these  are 
essentially  the  branches  of  the  trigeminus.  This  function  is 
best  shown  by  experiments  on  the  nerve  fibre  called  the 
lingual^  which  is  a  branch  of  the  inferior  maxillary;  but  the 
glosso-pharyngeal  and  pneumo-gastric  nerves  also  take  part 
in  the  centripetal  conduction;  for  excitations  of  the  stomach 
cause  secretion  of  the  saliva,  and  we  know  that  vomiting  is 

1  See  E.  Ritter,  "  Des  Phenomenes  Chimiques  de  la  Digestion." 
Th^se  de  Coricours,  Strasbourg,  1SG6. 

2  CI.  Bernard  believed  that  he  had  proved  that  the  sub-maxil- 
lary ganglion  may  serve  as  a  centre  of  salivary  secretion,  and  this 
was  generally  considered  a  sufficient  reason  for  asserting  that 
the  gangUons  of  the  great  sympathetic  nerve  possess  the  property 
of  reflex  centres;  but  this  opinion  can  no  longer  be  held  in  the 
presence  of  Schiif's  contradictory  experiments.  (See  Schiff, 
*'  Lemons  sur  la  Physiologie  de  la  Digestion."     Florence,  18 J6.) 


SALIVATION.  219 

always  preceded  by  an  increase  of  saliva.  If  a  section  of 
the  lingual  be  made,  we  find  that  irritation  of  the  peripheral 
part  of  the  nerve  which  has  been  cut  produces  no  effect  on 
the  formation  of  the  saliva,  while  excitation  of  the  central 
extremity,  which  is  still  connected  with  the  spinal  cord,  is 
certain  to  excite  the  secretion.  The  nerves  which  extend 
from  the  bulb  to  the  salivary  glands,  are  fibres  of  the  facial 
nerve,  especially  tlie  chorda  tympani:  this  latter  nerve  be- 
longs particularly  to  the  sub-maxillary  gland. 

Excitation  of  the  great  sympathetic  nerv-e  may  also  cause 
secretion  of  the  saliva,  but  this  does  not  appear  to  take  place 
normally,  under  reflex  influence.  The  saliva  produced  in 
experiments,  by  the  action  of  the  great  sympathetic  nerve,  is 
much  thicker  than  the  normal  saliva.  This  fact  must  be 
compared  with  what  takes  place  at  the  same  time  in  the 
vessels:  when  the  great  sympathetic  nerve  is  excited  the 
vessels  of  the  gland  become  constricted  (contracted),  while 
the  contact  and  exchange  between  the  blood  and  the  secre- 
tory elements  appear  more  intimate,  since  the  blood  which 
flows  from  the  gland  is  found  to  be  quite  black.  On  the 
other  hand,  when  the  sub-maxillary  gland  secretes  its  fluid 
])roducts,  under  the  influence  of  the  facial  nerve  (chorda 
tympani),  we  find  the  blood-vessels  greatly  dilated  (para- 
lyzed) and  the  blood  which  flows  from  them  red,  almost  as 
in  the  arterial  system  (CI.  Bernard). 

Too  much  importance  must  not,  however,  be  ascribed  to 
the  presence  of  the  blood  and  the  state  of  the  vessels ;  we 
have  already  shown  that  the  secretion  of  the  saliva  is  an 
instance  of  the  immense  attraction  exercised  by  the  secretory 
globule  over  the  surrounding  substances.  If  the  circulation 
be  suppressed,  we  may,  by  irritating  the  centripetal  or  cen- 
trifugal nerves  of  the  glands,  cause  the  production  of  a 
considerable  quantity  of  saliva  (Ludwig).  The  globule  then 
imbibes  the  materials  for  its  support  from  the  tissues  which 
surround  it :  it  possesses  great  power  of  attraction,  by  which 
it  gives  rise  to  the  currents  flowing  towards  it,  across  the 
inert  membrane  which  forms  the  coat  of  the  secretory  tubes. 

Thus  the  state  of  arterial  pressure  is  only  secondary.  The 
saliva  is  the  result  of  a  deliquium  of  the  cellular  elements  of 
the  glandular  epithelium,  and  in  this  case  we  cannot  con- 
sider the  gland  as  a  mere  filter.^     This  deliquium  is  pro- 

1  V.  Billet,  "  Gcndralite's  sur  les  Secretions."  These  de  Stras- 
bourg, 18(38,  No.  129. 


220  DIGESTIVE   SYSTEM. 

duced  by  the  action  of  the  nervous  system,  and  nervous 
terminal  ramifications  have  lately  been  discovered,  penetrat- 
ing the  glandular  epithelial  element  (Pfluger). 

Many  physiologists  maintain  that  the  nerves  affect  the 
secretion  of  the  saliva  only  by  their  function  as  vaso-motors. 
The  question  of  the  vaso-motor  nerves  that  cause  dilatation  of 
the  vessels  (see  p.  173)  here  again  presents  itself.  The  belief 
is,  however,  constantly  growing  into  favor,  that  the  intiuence 
of  the  nervous  system  on  secretion  bears  directly  on  the  glob- 
ular elements  of  the  secretory  pouches  or  bags  {ciels  de  sac),  but 
we  must  add  that  Pfluger's  researches  on  the  subject  of  the 
termination  of  the  nerves  in  the  glands  are  by  no  means  calcu- 
lated to  produce  conviction:  this histologist  supposes  that  the 
nerve  branches  terminate  in  the  so-called  glandular  culs-de- 
sac,  preserving  even  here  their  central  nerve  substance  (mye- 
line) ;  were  this  the  case,  it  would  bean  exception  to  the  general 
rule,  for,  when  a  nervous  filament  approaches  its  real  termina- 
tion, it  usually  lays  aside  its  myeline,  retaining  only  its 
axis-cylinder,  and  sheath  of  Schwann.  This  fact  leads  us  to 
suppose  that  Pfluger  did  not  discover  the  real  terminations 
of  the  secretory  nerves. 

On  the  other  hand,  histologists  have  made  great  efforts  to 
observe  the  act  of  fusion  of  the  globular  elements  of  secretion 
at  the  moment  when  this  takes  place,  or  at  least  to  ascertain 
what  changes  appear  in  the  epithelium  of  the  glands  after 
abundant  secretion :  Boll,  Giamiuzzi,  and  more  particularly 
Heidenhain  and  Ranvier,  devoted  themselves  to  the  study  of 
this  subject.  Giannnzzi  discovered  in  the  salivary  cells  peculiar 
prolongations  in  the  form  of  pedicles,  which  are  bent  round 
in  a  curve,  and  joined  on  to  the  enveloping  membrane :  he 
found  also,  in  the  glandular  culs-de-sac,  between  the  envel- 
oping membrane  and  the  salivary  cells,  properly  so  called, 
these  peculiar  formations  he  calls  half-moons  (or  crescents) 
being  special  cells,  flattened  in  shape,  and  with  one  or  two 
nuclei  (in  course  of  proliferation).  The  purpose  of  these 
elements  is  not  known.  Heidenhain  has  observed  that  we 
find  in  a  gland,  after  abundant  secretion,  in  place  of  the 
large  salivary  cells,  some  which  are  much  smaller  and  quite 
granular ;  he  supposes  that  the  larger  cells  are  destroyed  in 
order  to  form  the  substance  to  be  secreted,  that  the  remains 
escape  with  the  salivary  fluid,-  that  the  small  new  elements 
arise  from  Giannuzzi's  crescents,  and  that  these  are  in- 
tended to  take  the  place  of  the  salivary  globules  which  liave 
been  destroyed.     Ranvier  states  that  after  abundant  bccre- 


SALIVATION.  221 

tion  the  glandular  cuh-de-sac  decrease  somewhat  in  size,  and 
that  the  mucous  (salivary)  cells  empty  their  contents  grad^^ 
ually  without  being  destroyed.  "  In  short,"  he  says,  "  the 
product  secreted  by  the  glands  nrises  from  their  cells,  in  order 
to  form  which  the  glandular  cells  simply  yield  up  the  sub- 
stance which  has  been  elaborated  within  them,  and  are  not 
entirely  dcLslroyed,  as  Heidenhain  has  affirmed.  Their  active 
part  (nucleus  and  protoplasm)  still  remains,  and  it  is  this, 
j)robably,  which  makes  up  for  the  waste  occasioned  by  secre- 
tion.^ 

Some  agents  may  cause  secretion  of  the  saliva  by  exciting 
metamorphoses  of  the  epithelium  of  the  gland,  as  they  excite 
those  of  the  epithelium  of  the  mouth  in  general :  it  is  in  this 
way  that  mercurial  salivation  is  produced. 

The  excretory  tubes  of  the  salivary  glands  appear  to  be 
deficient  in  muscular  elements :  the  saliva  flows,  not  by  a 
movement  similar  to  the  peristaltic  movement,  but  by  a  sort 
of  vis  a  tergo  of  the  fluid,  which,  first  filling  the  lower  part 
of  the  salivary  tubes,  rises  gradually,  and  at  length  over- 
flows. 

The  nerve  centre  of  the  salivary  secretion  is  found,  as  we 
have  said,  in  the  spinal  cord ;  under  certain  circumstances 
the  intervention  of  other  nerve  centres  must  be  admitted : 
the  encephalon,  as  the  organ  of  the  imagination,  has  great 
effect  on  the  secretion,  and  the  sight  or  mere  remembrance 
of  food  will  suffice  to  increase  the  effect.  Still,  pro|)erly 
speaking,  the  will  has  no  power  to  produce  this  secretion : 
the  imagination  must  call  up  the  memory  of  a  gustatory 
impression,  or  produce  movements  in  the  mouth  which  are 
capable  of  producing  secretion  by  means  of  reflex  mechan- 
ism. Under  different  circumstances,  the  encephalon  appears, 
on  the  contrary,  to  act  against  secretion  by  paralyzing  the 
excitatory  nerves.  Thus,  certain  emotions  of  the  mind  will 
hinder  the  secretion  of  the  saliva,  while  others  increase  it. 
Strong  emotions  produce  this  effect ;  which  is  shown  by  ex- 
cessive dryness  of  the  mouth,  and,  sometimes,  almost  entire 
inability  to  s|)eak. 

The  secretion  of  the  saliva  is  also  more  or  less  under  the 
mechanical  influence  of  the  neighboring  organs:  thus  the 
movements  of  the  jaw,  and  contraction  of  the  muscles  of  the 

^  Ranvier,  "  Notes  a  la  Traduction  Franraise  de  THistologie  de 
Frey,"  p.  439. 


222  DIGESTIVE  SYSTEM. 

velum  of  the  palate,  by  acting  on  the  corresponding  glands, 
cause  secretion  of  the  saliva. 

Beside  tlie  chemical  effects  resulting  from  the  presence  of 
the  ptyaline  or  animal  diastase,  the  principal  use  of  the 
saliva  is  found  in  the  mechanical  part  which  it  takes  in 
mastication,  the  solution  of  sapid  substances,  the  lubrication 
of  the  passages  which  the  food  must  traverse  and  of  the  food 
itself.  We  shall  presently  see  that  the  saliva  is  essential  to 
deglutition  ;  for  this  purpose,  it  must  accompany  even  those 
aliments  which  are  not  chewed,  and  upon  which  it  produces 
no  chemical  effect.  This  explains  the  presence  of  the  salivary 
glands  in  the  carnivorous  animals,  in  which  the  saliva  is 
called  upon  to  act  on  aliments  which  are  essentially  nitro- 
genous. 

CI.  Bernard,  perhaps  a  little  exaggerating  the  mechanical 
property  of  the  salivary  fluid,  at  the  expense  of  its  chemical 
function,  assigns  to  each  saliva  a  peculiar,  corresponding, 
mechanical  function,  associating  each  of  them  with  one  of 
the  three  physiological  phenomena  of  mastication,  deglutition, 
and  gustation. 

The  parotid  is  the  masticatory  gland :  it  exists  only  in 
animals  which  have  teeth  to  grind  their  food ;  it  is  found  to 
be  larger  as  trituration  is  slower  and  more  difficult;  finally, 
the  parotid  secretion  takes  place  especially  during  the  move- 
ments of  mastication ;  and  when  the  animal  chews,  first  on 
one  side  and  then  on  the  other,  the  parotid  situated  on  the 
masticating  side  always  secretes  most  abundantly  (Colin) .^ 

The  eub-maxillary  secretion  belongs  only  to  the  phenome- 
non of  gustation :  the  most  certain  method  of  producing  this 
secretion  in  experiments  is  to  place  a  sapid  substance  on  the 
tongue,  and  thus  to  excite  the  reflex  action  which  we  have 
described  above ;  in  comparative  anatomy  we  find  that  the 
sub-maxillary  gland  disappears  wherever  there  is  no  need  of 
gustation:  it  is  largely  developed  in  the  carnivorous  ani- 
mals, while  it  disappears  almost  entirely  in  the  granivorous 
birds. 

Finally,  the  sub-lingual  gland,  the  secreted  product  of 
which  is  thick,  ropy,  and  similar  to  that  of  the  different 
buccal  glands,  called  mucous,  in  the  same  way  is  more  par- 
ticularly connected  with  deglutition :  it  serves  to  unite  the 

1  Colin,  *'  Traits  de  Physiologie  comparee  des  Animaux.'* 
2d  edition.     Paris,  1871,  Vol.  I.  p.  601. 


DEGLUTITION.  223 

elements  of  the  food  received,  and  to  lubric.ate  their  passage 
along  the  tongue,  and  the  isthmus  of  the  fauces. 

Tliese  distinctions,  which  appear  so  ingenious  and  natural  at 
first  sight,  SchifF  has  shown  to  be,  perhaps,  a  little  too  sharply 
defined;  thus,  mastication  alone,  —  that  is,  not  accompanied 
by  any  gustatory  impression,  —  has  little  or  no  influence  on 
the  parotid  secretion  :  in  the  case  of  all  the  salivary  glands, 
the  impression  of  taste,  joined  to  the  masticatory  movements, 
are  the  most  powerful  means  of  producing  secretion. 

The  quantity  of  saliva  secreted  in  a  day  has  been  variously 
estimated  on  account  of  the  intermittent  form  of  secretion. 
In  dogs,  it  is  as  much  as  1500  grammes.  This  secretion 
though  more  especially  sensible  during  mastication,  however, 
is  continuous;  because  the  saliva  is  necessary  to  keep  the 
mouth  moist,  to  assist  the  movements  of  the  tongue  (speech), 
and,  as  we  have  already  said,  for  the  purpose  of  deglutition. 
We  shall  find  that,  by  means  of  the  saliva,  movements  of 
deglutition  are  produced  from  time  to  time  and  at  very  short 
intervals,  the  purpose  of  which  is  to  preserve  the  function  of 
the  organ  of  hearing. 

C.  Deglutition. 

When  the  food  has  been  so  mixed  with  the  saliva  as  to 
become  capable  of  movements  like  a  fluid,  it  is  subjected 
to  a  pressure,  which  forces  it  downwards,  from  the  buccal 
cavity  to  the  cardiac  orifice  of  the  stomach;  in  other  words, 
it  leaves  the  mouth,  and  passes  through  the  pharyngeal  and 
(Esophageal  tubes.  The  principle  governing  the  movement 
of  the  food  is  the  same  as  that  which  governs  the  movement 
of  fluids,  that  is,  excessive  pressure  at  one  point  and  none  at 
all  at  others,  thus  destroying  the  equilibrium  of  the  fluid, 
and  causing  it  to  flow  in  the  direction  in  which  the  pressure 
is  slightest.  This  principle  applies  to  the  deglutition  of 
solids,  the  state  of  semi-liquefaction  into  which  they  are 
brought  imparting  to  them  mechanical  properties  similar  to 
those  of  fluids. 

The  organs  of  deglutition  consist  (Fig.  62),  first  of  the 
buccal  cavity, — bounded,  above,  by  the  roof  of  the  mouth; 
at  the  back,  by  the  velum  of  the  palate;  below,  by  the  tongue ; 
and,  in  front,  by  the  teeth.  After  the  buccal  cavity,  we  come 
to  the  pharynx,  at  the  level  of  which  the  alimentary  canal 
communicates  with  the  windpipe ;  or,  rather  the  two  passages 
cross  each  other  (communication  from  above  and  behind 
with  the  nasal  chambers  —  the  first  part  of  the  air  passage; 


224 


DIGESTIVE  SYSTEM. 


below,  and  in  front,  with  the  larynx  —  continuation  of  the 
air  passage).    A  most  important  feature  in  deglutition  is  the 


Fig.  62.  —  Mouth  and  pharynx.* 

mechanism  by  which  the  upper  and  the  lower  orifices  of  com- 
munication become  obliterated. 

When  mastication  and  insalivation  are  completed,  the 
food  collects  in  a  single  mass  on  the  surface  of  the  tongue, 
the  tip  of  which  touches  the  roof  of  the  mouth  while  the 


*  k,  h,  Buccal  aperture.  I,  Tongue,  rf,  Lower  jaw,  with  the  genio-glossal 
inserted,  e,  Hyoid  bone,  y,  P2piglottis. . ./',  Cavity  of  the  larynx  (with  the 
opening  of  the  ventricles),  c,  Velum  palati.  «,  Anterior  pillar  of  the  uvula. 
V,  Posterior  pillar.  L  Tonsil,  s,  Narrow  part  of  the  pharynx,  connectecl  with 
the  oesophagus,  z,  Orifice  of  the  Eustachian  tube,  at  the  upper  part  of  the 
pharvnx.  >  ♦  ■ 


DEGLUTITWN. 


225 


food  passes  downwards  to  its  base.  As  the  food  reaches  the 
front  pillars  of  the  yelum  of  the  palate  —  being  pushed  into 
the  pharynx  by  the  tongue  laid  against  the  roof  of  the  mouth  — 
It  is  seized  by  the  pharynx,  which  rises  before  it,  on  account 
of  the  contraction  of  its  longitudinal  fibres.  The  circular 
fibres  of  this  muscular  tube  immediately  contract  successively, 
and  drive  the  food  before  them  into  the  oesophagus,  where  it 
continues  its  progress  by  means  of  a  similar  peristaltism  — 
that  is,  successive  contraction  of  the  circular  muscular  fibres, 
driving  the  food  before  them,  while  the  contraction  of  the 
longitudinal  fibres  draws  towards  it  those  parts  of  the  tube 
in  which  it  is  to  become  involved. 

While  the  food  crosses  the  pharynx,  the  two  communica- 
tions between  this  tube  and  the  windpipe  are  obliterated. 

The  upper  communication  (pharynx  and  nasal  chambers) 
is  not  obliterated  by  a  movement  of  the  velum  of  the  palate 
resembling  that  of  a  drawbridge,  as  was  for  a  long  time  sup- 
posed (Bichat)  ;  it  takes  place  by  means  of  the  posterior 
pillars  of  the  velum  of  the  palate.  In  order  to  effect  this 
obliteration,  the  pillars  approach  each  other :  while  the  mus- 
cular fibres  of  these  pillars  (pharyngeal  muscles)  are  directed 


Fig.  63. —Diagram,  showing  the  occlusion  of  tlie  naso-pharyngeal  passage,  by  the 
action  of  the  muscles  of  the  posterior  columns  {Staphylo-pharyngeaTs.)* 

obliquely,  downwards  and  backwards,  across  the  lateral  walls 
of  the  pharynx,  and  are  again  joined  together,  along  a  con- 
siderable part  of  the  posterior  median  line,  so  as  to  form  an 


*  A,  This  part  is  seen  in  profile.  N,  Nasal  cavity.  B,  Mouth.  L,  Tongue. 
B^  Epiglottis.    7,  Uvula.    P,  F,  Course  of  the  staphylo-pharyngeal  muscle. 

B,  Diagram  of  the  orifice,  enclosed  hy  the  two  s'taphylo-pharyngeals  as  by  a 
sphincter.  1  (P^,  In  the  state  of  repose.  2  (P'O,  Semi-occlusion.  3  (P"')* 
Perfect  occlusion.    /.  Uvula. 

15 


226  DIGESTIVE  SYSTEM. 

elliptic  sphincter,  in  an  oblique  line  from  front  to  back  and 
from  top  to  bottom.  (Fig.  6B.)  The  anterior  and  posterior 
extremities  of  this  elliptic  sphincter  being  nearly  fixed,  its 
orifice  can  only  be  obliterated  by  reducing  it  to  an  antero- 
posterior slit.  By  means  of  this  movement  the  two  sides  of 
the  velum  of  the  palate  resemble  two  curtains  drawn  to- 
gether, the  pharyngeal  muscles,  which  are  concave  when  in 
the  state  of  repose,  having  their  curve  reduced  to  a  straight 
line ;  and  representing  in  this  state  of  contraction  the  string 
of  the  bow  w^hich  they  represented  when  in  the  state  of 
repose  (Fig.  63 ;  B,  2)  ;  an  opening  still  remains,  however, 
more  or  less  wide,  but  this  is  obliterated  by  the  contractions 
of  the  middle  and  inferior  sphincters  of  the  pharynx.  The 
uvula,  finally,  is  intended  to  close  any  crack  which  may  still 
remain  open,  but  it  is  not  indispensable  (Fig.  63,  B,  3,  I). 
By  means  of  these  movements,  some  idea  of  which  was 
formed  by  Albinus  and  Sandifort,  though  they  have  been 
most  clearly  demonstrated  by  Gercly  and.  Dzondi,  the  occlu- 
sion of  the  isthmus  of  the  fauces  is  made  even  hermetical. 
Indeed,  if  the  nostrils  be  stopf)ed  up  during  deglutition,  we 
find  that  hearing  is  slightly  obstnicted.  This  is  because, 
during  the  succession  of  peristaltic  movements  of  the 
pharynx,  its  upper  part  is  inclined ;  and,  as  the  pharyngeal 
sphincter  still  remains  shut,  rarefaction  of  the  air  in  the 
nasal  chambers  ensues.^  But  as,  during  deglutition,  the  base 
of  the  velum  of  the  palate  is  stretched  out  and  fixed  by  the 
contraction  of  its  superior  muscles,  and  thus  opens  the  Eus- 
tachian tube,  it  follows  that  the  rarefaction  of  the  air  of  the 
nasal  chambers  is  communicated  to  the  tympanic  drum, 
and  kept  up  until  a  fresh  movement  of  deglutition  places 
this  drum  in  communication  with  the  freely  opened  nasal 

1  This  fact  of  the  rarefaction  of  the  air  suggested  to  Maissiat 
(1838)  a  singular  theory  of  deglutition,  which  has  been  refuted  by 
the  explanation  given  here.  Maissiat  maintained  that  when  deglu- 
tition takes  place  a  vacuum  is  formed  in  the  cavity  of  the  pharynx 
by  means  of  its  rising  and  subsequent  enlargement:  the  food  is 
precipitated  into  this  cavity  by  the  pressure  of  the  atmosj)here, 
forming  what  Maissiat  calls  the  involuntary  jerk  (saccade)  of  deglu- 
tition. 

This  phenomenon  does  occur;  but,  in  the  first  place,  it  is  not  in 
the  pharynx,  properly  so  called,  but  in  the  naso-pharyngeal  cavity; 
and,  in  the  second,  the  formation  of  this  vacuum  does  not  correspond 
with  the  rising  of  the  pharynx,  but  with  its  descent;  not  at  the  be- 
ginning, but  at  the  end,  of  deglutition. 


DEGLUTITION.  227 

chambers.  This  shows  how  complete  is  the  obliteration 
of  the  isthmus  of  the  fauces ;  and  it  may  also  be  shown  by- 
means  of  a  tube  communicating  at  one  end  with  the  nasal 
chambers  (the  nostrils  being  closely  pressed  against  the 
tube),  while  the  other  end  is  immersed  in  water  (experiment 
by  Maissiat)  :  at  each  movement  of  deglutition  the  water 
rises  in  the  tube,  on  account  of  the  rarefaction  of  the  air  of 
the  nasal  chambers  (by  the  descent  of  the  constricted  isthmus 
of  the  fauces)  ;  this  rarefaction  is  communicated  to  the  air 
in  the  tube,  as  it  is  to  that  in  the  hollow  of  the  tympanum. 

The  isthmus  of  the  fauces  thus  undergoes  a  triple  change 
during  deglutition :  it  closes  by  the  contraction  of  its  con- 
strictors ;  it  rises  slightly  as  deglutition  begins;  and  descends 
slightly  as  this  is  finished.  This  rising  and  falling  is  produced 
by  the  simultaneous  movement  of  the  pharynx.  The  descent 
explains  the  vacuum  produced  in  the  closed  nasal  chambers: 
the  ascent  shows  us  why  a  probe  introduced  horizontally 
into  the  nasal  chambers,  as  far  back  as  possible,  will  be 
slightly  pushed  forward  as  each  movement  of  deglutition 
begins  (experiment  by  Debrou)  ;  this  led  Bichat  to  believe 
that  there  was  some  disarrangement  at  the  top  of  the  velum 
of  the  palate,  and  others  that  the  velum  is  simply  raised ;  but 
we  have  seen  that  not  only  the  velum,  but  the  whole  isthmus 
of  the  fauces  when  constricted,  rises  and  sinks  again  imme- 
diately. 

The  occlusion  of  the  antero-inferior  orifice  of  communica- 
tion, or  orifice  of  the  larynx,  is  effected  by  means  of  the 
epiglottis,  which,  when  free,  leaves  the  respiratory  orifice 
uncovered,  but,  as  it  is  formed  of  elastic  tissue,  bends  under 
the  weight  of  the  food  as  it  passes.  The  epiglottis  is  not, 
however,  indispensable  to  this  obliteration.  As  the  pharynx 
rises,  the  larynx,  sharing  the  movement,  strikes  against  the 
base  of  the  tongue  (which  is  there  protuberant),  and  this 
mechanism  is  sufficient  to  protect  the  respiratory  orifice,  or 
at  least  to  secure  the  retroversion  of  the  epiglottis  over  it. 
The  small  cartilages  placed  above  the  arytenoid  cartilages 
join  with  the  epiglottis  in  eff*ecting  the  occlusion  of  the 
opening  of  the  larynx. 

The  absence  of  the  epiglottis  is  scarcely  any  hinderance  to 
the  deglutition  of  solids  :  the  movements  of  the  whole  larynx 
under  the  cushion,  at  the  base  of  the  tongue,  suffice  to  pro- 
tect the  respiratory  orifice.  The  case  is  not  the  same,  how- 
ever, with  the  deglutition  of  fluids,  and  this  shows  us  the 
purpose  of  the  epiglottis.     When  the  deglutition  of  a  mass 


228  DIGESTIVE   SYSTEM. 

of  fluid  is  completed,  the  larynx  resumes  its  natural  position; 
but  some  drops  of  the  fluid  always  remain  on  the  back  of  the 
tongue,  and,  uniting  together,  flow  into  the  oesophagus; 
these  would  inevitably  fldl  into  the  larynx  but  f^r  its  mem- 
branous lid  (the  epiglottis).  Clinical  observations  and  the 
results  of  experiments,  however,  often  appear  contradictory 
on  this  point ;  since  we  find  that  sometimes  a  fit  of  coughing, 
and  at  others,  no  disturbance  at  all,  will  follow  the  degluti- 
tion of  a  fluid  in  invnlids  or  animals  who  have  been  deprived 
of  their  epiglottis  (Magendie,  Longet).  The  varying  nature 
of  these  results  is  easily  explained.  In  man,  the  epiglottis 
may  be  destroyed  by  so  many  different  causes  (wounds, 
syphilitic  erosions)  that  no  two  cases  can  be  compared,  and 
one  person  will  suffer  no  inconvenience,  while  in  another 
alarming  symptoms  will  follow  the  deglutition  of  a  fluid. 
The  different  results  produced  in  animals  by  the  deglutition 
of  fluids,  after  the  epiglottis  has  been  carefully  removed,  is 
explained  by  the  fact  that,  whenever  the  animal  is  calm  after 
deglutition,  no  disturbance  follows,  while  serious  conse- 
quences ensue  if  it  is  agitated  in  any  way.  Schiff"  has  demon- 
strated that,  when  the  deglutition  of  fluids  is  apparently  fin- 
ished, the  accumulation  of  drops  remaining  on  the  tongue, 
which  descends  to  the  glosso-epiglottal  ligaments,  gives  rise 
to  a  second  series  of  movements  of  deglutition,  repeated  two 
or  three  times,  until  not  a  drop  of  the  fluid  remains.  Now, 
if  an  animal  be  disturbed  while  drinking,  in  however  slight  a 
degree  (as,  for  instance  a  dog  may  be  prevented  from  licking 
himself,  after  swallowing  a  bowlful  of  milk)  this  secondary 
deglutition  does  not  take  place,  and  if  the  epiglottis  have 
been  removed,  the  drops  ot  fluid  remaining  on  the  tongue, 
may  be  introduced  into  the  larynx,  and  occasion  coughing. 
In  short,  entire  excision  of  the  epiglottis  in  the  dog,  does 
not  interfere  with  the  deglutition  of  fluids,  if  only  that  sub- 
sequent deglutition  takes  place,  which  serves  to  rid  the  isth- 
mus of  the  fauces  of  those  fluid  particles  which  still  adhere 
to  it. 

Though  solid  or  liquid  particles  of  food  sometimes  find 
their  way  into  the  larynx,  it  rarely  happens  that  they  pene- 
trate into  the  trachea:  as  soon  as  they  come  into  contact 
with  the  mucous  membrane  of  the  vestibule  of  the  larynx, 
the  peculiar  sensibility  which  the  superior  laryngeal  nerve 
imparts  to  this  region  is  excited,  giving  rise  to  the  phenom- 
enon of  coughing,  by  means  of  which  these  particles  are 
instantly  expelled.     The  exquisite  sensibility  of  the  vestibule 


DEGLUTITION.  229 

of  the  larynx  thus  has  an  important  share  in  the  protection 
of  the  respiratory  organs  (Longet) ;  it  is  intended  to  prevent 
the  entrance  of  foreign  bodies  into  these  organs,  an  occur- 
rence which  the  animal  would  have  no  power  to  prevent,  if 
the  opening  of  the  glottis  were  once  passed  (see  larynx  and 
obtuse  sensibility  of  the  trachea). 

A  final  obstacle  to  the  entrance  of  these  bodies  into  the 
trachea  is  found  in  the  fact  that  the  opening  of  the  glottis 
closes  whenever  deglutition  takes  place;  this  occlusion  is, 
however,  only  a  precautionary  measure  ;  and  it  must  not  be 
supposed  that,  in  the  normal  state,  the  substances  which  are 
being  swallowed  come  in  contact  with  the  edges  of  the  glot- 
tis. Magendie,  who  first  discovered  this  closure  of  the  glottis 
during  deglutition,  attached  too  much  importance  to  it,  and 
was  mistaken  as  to  the  mechanism  by  which  it  is  produced, 
attributing  it  to  the  muscles  of  the  larynx,  in  this  special 
case  (arytenoid,  aryteno-epiglottidean)  innervated  by  the 
upper  laryngeal  nerve.  Longet,  who  understood  the  subject, 
has  shown  both  the  accessory  importance  of  this  occlusion 
and  its  mechanism,  which  consists  in  the  movement  of  the 
thyroid  cartilage  by  means  of  the  contmction  of  the  sphincter 
muscles  of  the  pharynx.  The  movements  of  the  glottis 
accompanying  deglutitio7i  are  thus  subjected  to  other  m,uscu- 
lar  agents  than  those  which  act  upon  this  same  orifice^  dur- 
ing the  production  of  the  vocal  and  respiratory  phenom^ena, 
(Longet).  Finally,  Claude  Bernard  has  completed  the  study 
of  this  interesting  question,  which  here  we  can  only  sum  up 
rapidly,  by  showing  that  the  spinal  accessory  nerve  inner- 
vates the  inferior  constrictor  muscle  of  the  pharynx  in 
order  to  produce  this  occlusion  of  the  glottis ;  and  we  can 
thus  add  to  Longet's  conclusion,  that  the  nerves  which  pre- 
side over  this  occlusion  of  the  glottis  ^uring  deglutition  are 
not  the  same  as  those  which  govern  its  respiratory  move- 
ments ;  they  are  the  filaments  from  the  spinal  accessory  nerve, 
whose  influence  here,  as  in  all  its  other  functions,  is  opposed 
to  that  of  the  pneumogastric  nerve  (CI.  Bernard). 

A  very  important  part  of  the  physiology  of  deglutition  is 
the  way  in  which  it  is  directed  by  the  nervous  system :  de- 
glutition is  one  of  the  most  striking  examples  of  reflex  influ- 
ence. We  cannot  simply  swallow,  without  giving  rise  to  a 
local  excitation,  which  serves  as  a  point  of  departure  of  the 
reflex  action :  there  must  be  some  substance  in  the  mouth,  a 
small  portion  of  food  or  of  saliva ;  and,  when  we  fancy 
that  we  are  swallowing  nothing,  the  movement  is  really  for 


280  DIGESTIVE   SYSTEM, 

the  purpose  of  conveying  the  drops  of  saliva  into  the 
throat,  where  their  presence  excites  the  reflex  action.  The 
will  is  likewise  i)Owerless  to  prevent  deglutition,  which  latter 
continues,  even  if  a  body  dangerous  to  life  is  brought  in  con- 
tact with  this  region.  Finally,  the  most  remarkable  fact  is 
that  the  act  of  sw\allovving  must  begin  at  the  beginning :  if 
the  food  be  stoi)ped  in  its  course,  it  can  continue  only  by 
means  of  a  fresh  movement  of  deglutition,  commencing  at 
the  isthmus  of  the  fauces. 

The  spinal  cord  is  the  centre  of  these  nei*vous  phenomena 
whose  centripetal  organs  are  the  sensory  branches  of  the  tri- 
geminus, the  glosso-pharyngeal,  and  the  superior  laryngeal 
nerves;  the  centrifugal  nerves  are  the  motor  branches  of 
the  glosso-pharyngeal,  and  the  pneumogastric  nerves,  re-en- 
forced by  anastomoses  with  the  flicial  and  the  spinal  nerve. 

The  will  being  powerless  to  produce  this  phenomenon,  we 
see  that  the  brain  has  no  share  in  it :  thus  the  act  of  swal- 
lowing may  be  excited  in  persons  under  the  influence  of 
narcotics,  or  in  animals  whose  brain  has  been  removed. 

The  region  of  the  isthmus  of  the  fauces  may  also  be  the 
centre  of  anti-peristaltic  movements,  accompanied  by  dis- 
agreeable sensations  (disgust)  and  causing  vomiting  (nausea); 
for  this  reason  the  glosso-pharyngeal  nerve,  which  appears  to 
be  the  special  conductor  of  the  sensations,  is  sometimes 
called  the  nerve  of  nausea. 

The  normal  execution  of  the  reflex  action  of  deglutition 
also  appears  to  require  that  the  epithelium  of  the  isthmus  of 
the  fauces  shall  be  in  a  sound  state.  This  epithelium  often 
suffers  from  atrophy,  and,  on  account  of  this,  the  sensibility 
of  the  part  is  impaired,  and  the  reflex  action  consequently 
rendered  difticult  or  impossible,  from  feilure  of  the  impres- 
sion which  gives  rise^to  it :  this  is  the  reason  that,  in  chronic 
diseases,  we  see  persons  die  —  or,  rather,  let  themselves  die  — 
of  hunger,  because  the  act  of  swallowing  has  becomie  too 
painful. 

The  epitheliumof  the  supra-diaphragmatic  portion  of  the 
digestive  canal  is  generally  of  great  im|>ortance  in  pathology: 
in  some  cases  of  disease  it  thickens  and  falls  off",  causing  the 
furred  coating  of  the  mouth.  This  abnormal  growth  is  only 
an  exaggeration  of  what  takes  place  in  a  normal  condition  in 
certain  parts,  in  the  tonsil,  for  instance.  The  base  of  this 
organ  is  formed  of  elements  similar  to  those  of  the  lymphatic 
ibllicles ;  but  numerous  prolongations  in  culs-de-sac  proceed 
to  it  from  the  buccal  epithelium,  making  its  structure  spongy, 


DIGESTIVE  TUBE. 


281 


similar  to  that  of  a  irland  :  these  prolongations  are  filled  with 
epithelial  detritus,  the  odor  of  which  is  often  very  offensive. 
The  epithelium  of  the  remaining  portions  of  the  buccal 
cavity  is  simple,  but  not  less  important  on  that  account.  We 
shall  find  that  it  forms  a  considerable  part  of  the  structure 
of  the  papillaB  of  the  tongue,  the  organs  of  the  sense  of 
taste.  It  is  this  which,  when  covered  with  calcareous  sub- 
stances, changes  into  enamel^  a  layer  of  prismatic  elements 
forming  a  resisting  covering  for  the  surface  of  the  teeth ;  and, 
by  a  similar  transformation,  produces  whalebone  or  fins  in  the 
young  cetaceans.  Finally,  we  have  seen  that  the  salivary 
glands  are  the  seat  of  deep  and  more  or  less  considerable 
giowths  of  this  epithelium. 

III.   Sub-diaphragmatic  Portion  op  the  Digestive 
Tube. 

The  sub-diaphragmatic  part  of  the  digestive  tube  proceeds 
from  the  internal  or  mucous  fold  of  the  blastoderm  by  means 
of  the  folding  in  which  the  body  of  the  embryo  undergoes 


Fig.  64.  —Formation  of  the  intestinal  tube.* 

at  the  two  extremities  and  at  the  sides.  Its  primitive  cavity 
is  divided  in  two :  on  the  one  side  the  umbilical  vesicle  (see 
farther  on,  Embryology)^  and  on  the  other  a  middle  tube, 


*  A,  B,  C,  Different  degrees  of  development  of  the  stomach  and  of  the  con- 
volutions of  the  intestine,  pvoperlv  so  called,  s,  Stomach.  /,  S  iliac,  o,  Om- 
phalo-mesenteviatube.  6,  I'ouch  from  which  th<^  caecum  is  aftenvards  formed, 
c,  Colon,    k^  Convolutions  of  the  small  intestine. 


232  DIGESTIVE  SYSTEM, 

which  is  at  first  cylindrical  and  of  an  uniform  calibre 
(Fig.  64,  A).  The  upper  part  of  this  intestine,  however, 
soon  dilates  (Fig.  64,  A,  s),  and  then  becomes  obhque; 
so  that  its  lower  extremity,  which  is  the  least  dilated  (Fig. 
64,  B,  d),  is  turned  to  the  right,  while  the  left  side  becomes 
anterior.  The  stomach  is  thus  formed  (Fig.  64,  C,  s,  d),  and 
in  the  same  way  the  pneumogastric  nerve  becomes  ante- 
rior as  it  passes  below  the  diaphragm.  The  rest  of  the 
digestive  tube  lengthens  out,  and,  consequently,  is  separated 
from  the  vertebral  column,  and  forms  a  loop :  the  tube,  by 
means  of  which  the  intestine  communicates  with  the  umbili- 
cal vesicle,  begins  at  the  summit  of  this  loop  (Fig.  64,  B,  o). 
The  upper  branch  of  the  loop  is  placed  anteriorly,  and  soon 
exhibits  a  slight  swelling  (5),  which  is  the  first  appearance 
of  the  ccecum  and  of  the  ccBcal  appendix:  the  remaining 
portion  of  the  loop  forms  the  large  intestine^  as  far  as  the  sig- 
moid flexure  of  the  colon  (Fig.  64,  B,  6,/*,  and  C,  h^f\  c) ; 
while  the  convolutions  of  the  summit  and  postero-inferior 
portion  of  the  loop  are  developed  (Fig.  64,  B,  A;),  and  form 
the  small  intestine  (C,  Jc)} 

The  epithelium  of  this  part  of  the  digestive  tube  is  colum- 
nar throughout,  and  is  continued  at  its  two  extremities 
with  the  pavement  epitheliums  of  the  oesophagus  and  of  the 
skin.  It  also  forms  outgrowths  on  the  surface  {or  phaneres) 
and  in  the  deeper  tissues  (or  crypts).  The  former  are  repre- 
sented by  the  villosities,  which  we  shall  study  in  regard  to 
the  subject  of  absorption ;  the  latter  are  the  various  glands 
of  the  intestinal  tube.  Some  of  these  glands  are  extremely 
simple,  as  the  follicles  or  glands  of  Lieberkuhn,  which  are 
only  a  depression  like  the  finger  of  a  glove  (Fig.  65),  and 
are  found  throughout  this  portion  of  the  alimentary  canal ; 
in  the  stomach,  however,  some  of  these  depressions  have  a 
complex  structure,  and  the  epithelium  of  their  caecal  extrem- 
ity is  no  longer  columnar ;  we  have  also  the  peptic  (/lands. 
Farther  on,  a  still  more  complex  growth  gives  us  glands  in 
clusters,  such  as  the  glands  of  ^runner,  in  the  duodenum : 
the  pancreas  is  only  a  huge  gland  of  this  class.  Fin.Uly, 
embryology  shows  us  that  the  liver  is  itself  formed  of  i)ouches 
similar  to  those  of  the  glands  of  Lieberkuhn,  but  very  long, 
and  so  spacious  that  between  them  is  found  another  glan- 
dular organ,  arising  from   the   growth  of  the  coats  of  the 

1  See  K.  Vierordt,  "  Grundriss  der  Physiologie  des  Menschen." 
Francfort,  18G0,  p.  420. 


STOMACHAL  DIGESTION, 


233 


omphalo-mesenteric  vein  (later  becoming  tlie  portal  vein). 
The  liver  is  thus  formed  by  the  junction  of  two  organs:  first, 
the  biliary  liver,  formed  of  tubes 
lined  with  a  columnar  epitheli- 
um, such  as  the  glands  of  Lieber- 
kuhn ;  and,  second,  the  blood 
liver,  constituted  by  the  real  acini 
of  the  liver  (around  which  are 
placed  the  biliary  culs-de-sac) ; 
the  purpose  of  these  is  to  elabo- 
rate the  blood,  and  especially  to 
introduce  into  it  sugar  or  glyco- 
genous  matter;  whence  the  name 
of  glycogenic  liver,  though  the 
presence  of  sugar  is  not  peculiar 
to  the  tissue  of  the  liver. 

These  different  glands  pour 
into  the  intestinal  tube  their 
secretory  products,  which  thus 
come  generally  in  contact  with 
the  alimentary  substances  re- 
ceived from  without:  these  sub- 
stances are  modified  by  the  fluids, 
and  at  the  same  time  subjected  ^^S-  65. -Tube-shaped  glands  of 

,  ^  ''      .  the  intestinal  mucous.* 

to  phenomena  oi .  transportation 

(peristaltic  movements)  by  means  of  the  muscular  coats  of 
the  stomach  and  intestines.  We  shall  study  these  chemical 
and  mechanical  phenomena  in  the  stomach  and  in  the  intes- 
tine, and  shall  see  how  the  larger  portion  of  the  substances 
which  are  thus  elaborated  is  absorbed  by  the  coats  of  the 
digestive  tube,  and  especially  by  its  epithelium;  and  also, 
finally,  how  the  residuum  of  the  aliments,  as  well  as  the  prod- 
ucts of  intestinal  desquamation,  are  rejected  after  passing 
through  the  large  intestine. 

A.  Stomach. 

The  stomach  is  a  poucli  intended  as  a  temporary  receptacle 
for  the  aliments  introduced  into  it  by  the  act  of  deglutition. 
Some  aliments  only  pass  through  the  stomach,  such  as,  in 
horses  especially,  those  fluids  which  accumulate  in  the  intes- 


mmm 


*  «7,  Thick  layer  of  glands.  6,  Tissue  belonging  to  the  mucous  and  the  cel- 
lular layer,  c,  Sub-mucous  tissue  traversed  by  the  vessels  cut  transversely,  d. 
Layer  of  the  circular  muscular  fibres,  e,  Longitudinal  fibres.  J,  Peritoneal  en- 
velope.   (KoUilver,  "  Histologic." ) 


234  DIGESTIVE  SYSTEM. 

tine.  Other  aliments  generally  remain  for  some  time  in  the 
stomach,  and  the  length  of  this  period  is  determined  by  the 
degree  of  difficulty  which  the  stomach  has  in  digesting  them ; 
those  aliments  which  it  cannot  attack  remaining  in  its  cavity 
as  long  as  possible. 

We  have  to  consider  in  the  stomach :  on  the  one  hand,  the 
motor  element  peculiarity ;  and,  on  the  other,  the  secretory  or 
epithelial  peculiarity. 

I.  The  motory  apparatus  consists  of  a  somewhat  slight 
fleshy  tunic,  which  rarely  contracts,  and  is  incapable  of  any 
great  exertion,  at  least  in  man  and  in  the  mammalia.  Those 
peristaltic  contractions  which,  by  means  of  a  sort  of  degluti- 
tion, carry  the  contents  of  the  stomach  from  the  cardia  to 
the  pylorus,  and  thence  into  the  intestine,  are  extremely 
gentle  and  slow ;  since  this  kind  of  deglutition  of  bodies  which 


Fig.  66.  —Muscular  (oblique)  fibres  of  the  stomacb  {cravate  de  suiase)  • 

are  sharp,  hard,  and  apparently  injurious,  has  been  known  to 
take  place  without  being  followed  by  any  bad  consequences. 
These  contractions  are  the  result  of  a  reHex  action  succeed- 
ing the  impression  made  upon  the  surface  of  the  stomach  by 
the  substances  received,  and  appear  thus  to  make  a  sort  of 
selection  of  those  which  are  to  remain  a  longer  or  shorter  time 
in  the  stomach.  Thus  fluids  do  not  accumulate  in  this  reser- 
voir, even  during  a  meal,  and  no  very  great  difference  is 

♦  The  stomach  appears  turned  over,  and  the  muscular  bands  are  fhown  by 
the  removal  of  the  mucous  coat.  1,  Circular  fibres  of  the  oesophagus.  2, 3,  Cir- 
cular libres  of  the  stomach.    5,  Cravate  de  Suisse. 


STOMACHAL  DIGESTION,  235 

found  to  exist  between  the  stomach  of  a  person  who  has 
drunk  and  that  of  one  who  has  not  drunk  while  eating. 
This  is  because  along  the  anterior  and  posterior  surfaces  of 
the  stomach  there  run  longitudinal  fibres  parallel  to  the 
smaller  curvature,  situated  at  some  distance  from  it,  and 
extending  from  one  surface  to  the  other,  below  the  cardia 
and  the  pylorus  (Fig.  68).  They  thus  form  a  sort  of  ellipti- 
cal ring  {cravate  de  srcisse)  or  sphincter,  which,  as  it  con- 
tracts, divides  the  stomach  in  two  parts  (Fig.  67) :  namely, 
the  region  of  the  greater  curvature 
(Fig.  67,  S),  hermetically  closed:  and  the 
region  of  the  smaller  curvature,  forming 

a  fube  which  leads  from  the  cardia  to  the  '^J l^— ^^  <ili^ 

pylorus;  this  canal  (Fig.  67,  L)  is  formed 
at  the  time  of  the  deglutition  of  fluids, 
and  these  follow  it;  so  that  degluti- 
tion may  be  said  to  continue  from  the 
pharynx  down  to  the  duodenum  with-  Fig.  67.-Appearance  caused 
out  their  properly  entering:  the  stomach  27  ^^®  contraction  of  the 
11  1      rill  •  .•  hajiA  Icravaiedesause).* 

at  all.*     1  bus,  m  a  person  presentmg 

an   abnormal   communication   of   the   duodenum   with   the 

colon,  the  ingestion  of  a  glass  of  water  has  been  observed  to 

^  See  R.  Larger,  "  Essai  Critique  et  Experimental  sur  les 
Muscles  Lisses  en  general  et  sur  quelques-uus  en  particulier  (Esto- 
mac).     These  de  Strasbourg,  1870,  No.  262. 

P.  59:  "  We  have  had  the  good  fortune  to  witness  the  contrac- 
tion of  the  oblique  fibres  of  the  stomach,  which  we  have  never 
succeeded  in  producing  artificially.  The  animal  was  a  dog.  We 
found  a  tolerably  deep  groove,  extending  from  the  cardia  to  the 
bend  of  the  stomach,  exactly  in  the  path  of  the  oblique  fibres 
(cravate  de  Suisse) ;  and,  singularly  enough,  at  the  same  time  the 
smaller  curvature  of  the  stomach  curved  outwards  in  a  most 
remarkable  manner.  This  condition  lasted  for  some  time,  and 
then  gradually  ceased,  but  a  few  moments  later  the  same  phenom- 
enon was  reproduced.  Another  remarkable  feature  consists  in  the 
relaxation  of  the  circular  fibres  in  that  part  situated  above  the 
band  of  oblique  fibres  during  the  contraction  of  the  lower  part. 
The  tube  which  we  saw  formed  was  not  complete  in  one  respect, 
that  is,  the  two  surfaces  of  the  stomach  were  not  united  below 
under  the  influence  of  the  contraction  of  the  oblique  fibres.     The 

*  A,  Vertical  section  of  the  stomach  in  the  state  of  repose,  m,  m,  Cravate 
de  Suisse. 

B,  Contraction  of  these  muscular  bundles  (wi,  to),  drawing  together  the  cor- 
responding parts  of  the  coat  of  the  stomach,  in  the  direction  indicated  by  the 
arrows,  and  thus  dividing  the  cavity  into  two  parts  (S  and  L). 


236  DIGESTIVE  SYSTEM. 

be  instantly  followed  by  liquid  stools,  the  water  which  enters 
the  great  intestine  directly  after  being  swallowed  producing 
the  effect  of  an  injection. 

Vomiting.  —  Apart  from  this  peculiar  function  of  the  mus- 
cular necklace  or  band  placed  along  the  smaller  curvature, 
the  mechanical  role  of  the  muscular  coats  is,  as  we  have  said, 
of  little  importance.  Thus,  the  stomach  takes  scarcely  any 
part  in  the  movements  of  regurgitation  made  in  vomiting : 
it  rejects  its  contents  under  the  influence  of  the  pressure  ex- 
ercised by  the  diaphragm  and  the  muscles  of  the  abdominal 
coats.  Kecent  investigations  by  Schiff,  however,  show  that 
if  the  muscular  coat  or  tnnic  of  the  stomach  does  not  pro- 
duce the  effort  of  vomiting,  in  order  to  throw  off  the  con- 
tents of  the  viscera,  it  at  least  serves  to  aid  in  this  rejection. 
To  this  end  the  longitudinal  fibres  of  the  cardiac  region  con- 
tract, and  then,  straightening  their  curve,  distend  the  corre- 
sponding orifice.  Tlie  attempt  to  vomit  succeeds  only  when 
the  abdominal  pressure  takes  place  simultaneously  with  this 
dilatation  of  the  cnrdia.  The  pneumo-gastric  nerve  regulates 
the  association  of  these  movements.^ 

Vomiting  is  a  reflex  action  resembling  that  of  sneezing. 
(See  p.  47.)  The  agents  by  which  it  is  excited  act  upon  the 
nerve  centres  either  directly,  or  by  the  intervention  of  various 
sensory  nerves,  as  the  pneumo-gastric  and  the  glosso-pharyn- 
geal  nerves.  Those  which  act  by  means  of  this  latter  nerve, 
are  called  nauseous  (see  sense  of  taste ;  the  glosso-pharyngeal 
a  nauseous  nerve)  the  rest  are  simply  vomitive. 

II.  The  columnar  epithelium  of  the  stomach  exerts  a  pro- 
tecting influence  over  this  viscus :  and  prevents  it  from 
digesting  itself;  but,  if  the  epithelium  be  injured  in  any  part, 
the  gastric  juice  acts  upon  the  subjacent  parts  of  the  coats 
of  the  stomach,  producing  an  erosion  known  in  pathology 
under  the  name  of  round  ulcer.     The  epithelium  is  here,  as 

fluids,  however,  could  pass  with  the  greatest  ease  from  the  pylorus  to 
the  cai'dia,  or  inversely,  without  mine/ling  with  the  aliments  contained 
in  the  cardiac  portion,  the  latter  being  strongly  pressed  against  its 
contents,  which  it  thus  prevented  from  passing  out,  or  from  being 
penetrated  by  the  fluids. 

*'  This  fact  justifies  the  hypothesis  set  forth  by  Luschka,  and  by 
Professor  Kiiss  in  his  lectures,  which  attributes  to  the  oblique  fibres, 
in  certain  cases,  the  power  of  establishing  a  direct  communication 
between  the  orifices  of  the  cardia  and  the  pylorus." 

^  M.  Schiff,  '*  LcQons  snr  la  Physiologic  de  la  Digestion.'* 
1867,  Vol.  U.,  37th  legon. 


STOMACHAL  DIGESTION,  237 

on  so  many  other  surfaces  (the  bladder,  for  instance),  an 
obstacle  to  absorption ;  indeed,  it  has  been  demonstrated 
that,  in  spite  of  its  lymphatic  and  blood  vessels,  the  stomach 
does  not  absorb.  Experiments  have  been  made,  proving 
that  a  horse,  in  which  the  pylorus  has  been  tied,  is  not  poi- 
soned by  the  ingestion  of  a  considerable  dose  of  strychnine 
(experiments  by  Bouley),^  and  this  fact  has  been  found  to  be 
similar  in  regard  to  man.  Thus  a  case  has  been  known  in 
which  a  man,  suffering  from  obstruction  of  the  pylorus, 
experienced  constant  thirst,  in  spite  of  having  swallowed 
large  quantities  of  water;  it  was  shown  by  an  autopsy  that 
the  mucous  membrane  of  the  stomach  was  in  a  perfectly 
healthy  condition ;  here  thirst  was  relieved  by  the  injection 
of  water  into  the  rectum.  In  the  case  of  another  patient,  we 
have  seen  the  ingestion  of  opium  fail  entirely  of  its  usual 
calming  effect,  because  some  unknown  cause  prevented  the 
drug  passing  out  by  the  pyloric  orifice ;  in  this  case  a  large 
quantity  of  opium  was  administered,  and  the  obstruction  at 
the  pylorus  being  in  some  way  suddenly  removed,  symptoms 
of  poisoning  followed,  owing  to  the  large  quantity  of  opium 
accumulated  in  the  stomach,  which  was  afterwards  absorbed 
in  the  intestinal  canal.^ 

^  Bouley,  "  Bulletin  de  P Academic  de  Medecine."  1842,  Vol. 
XVII. 

2  The  question  of  absorption  by  the  stomach  has  been,  however, 
revived  by  recent  investigations.  Several  Italian  physiologists,  on 
repeating  Bouley's  experiments,  have  observed,  hke  him,  that  in 
the  horse  large  doses  of  strychnine  introduced  into  the  stomach, 
the  pylorus  having  been  previously  tied,  do  not  produce  poisoning. 
But  a  new  and  important  observation  has  been  made,  namely,  that 
neither  does  poisoning  take  place,  if,  after  a  considerable  interval, 
the  ligature  be  untied,  and  free  course  allowed  to  the  contents  of 
the  stomach.  According  to  Schiff,  this  latter  circumstance  indi- 
cates that  the  absorption  of  the  strychnine  has  been  sufficiently 
gi-adual  to  allow  of  its  being  proportionally  eliminated  by  the  urine, 
without  accumulating  in  the  blood  to  such  an  extent  as  to  pro- 
duce poisoning.  The  same  has  been  observed  with  woorara,  which 
is  also  absorbed  by  the  intestine,  but  so  slowly  that  it  is  eliminated 
by  the  kidneys  before  a  quantity  which  could  prove  fatal  has  had 
time  to  accumulate  in  the  organism  (CI.  Bernard).  For  further 
details  on  this  subject,  see  the  recent  publication  by  F.  Lussana: 
"  Sulla  Piccola  Circolazione  Entero-epatica,"  etc.  Lo  Speriraen- 
tale,  Octobre,  1872.  —  Analyzed  in  "  llevue  des  Sciences  Medi- 
cales,"  de  G.  Ilayem,  Vol.  I.,  p.  32. 

Schiff,  relying  on  various  experiments  made  by  himself  and  by 
Colin,  admits  absorption  by  the  stomach  as  a  general  fact.     Wo 


238 


DIGESTIVE  SYSTEM. 


The  principal  function  of  the  epithelium  of  the  stomach  is 
to  throw  out  the  products  of  secretion.  In  the  first  place, 
this  mucous  coat,  like  all  the  others,  supplies  mucus  by  des- 
quamation :  this  is  generally  found  in  flakes,  because  the 
shedding  of  the  epithelial  cells  is  not  complete ;  but  it 
appears  only  in  morbid,  or,  at  least,  abnormal  cases,  the  nor- 
mal gastric  juice  containing  no  mucus  ;  those  glands  of  the 
stomach  (identical  with   Lieberkuhn's  glands)    which  have 

been  called  mucous  glands^ 
have  thus  been  incorrectly 
named,  the  mucus  not  being 
a  normal  product,  and  no 
special  gland  being  needed 
to  produce  it.  Since  it  is 
the  result  of  desquamation 
of  the  entire  free  surface. 

The  normal  and  charac- 
teristic secretion  of  the 
stomach  is  the  gastric  juice, 
which  is  chiefly  produced  by 
the  glandular  culs-de-sac  of 
the  cardiac  region.  These 
are  distinguished  from  the 
ordinary  glands  of  Lieber- 
kuhn  (Fig.  65)  by  their 
epithelium  not  being  co- 
lumnar, but  polyhedral,  at 
least  in  the  deeper  portions 
(Fig.  m)}  This  gastric 
juice,  produced  by  the  shed- 
ding or  falling  off"  from 
these  cellular  elements,  is  a 
very  thin  fluid,  containing 
scarcely  four  per  cent  of  solid 
matter,  two-thirds  of  which  consist  of  organic  substances 


Fig.  68.  —  Compound  peptic  gland.* 


shall  see  that  such  absorption  is  necessary  to  his  theory  of  pepto- 
genous  substances,  which  we  shall  examine  later. 

1  Large  quantities  of  closed  follicles  (resembhng  those  of  the 
intestine)  recently  have  been  presumably  discovered  in  the  stomach, 

*  1,  Excretory  tube,  lined  with  a  columnar  epithelium  resembling  that  of  the 

fjastric  mucous  in  general.  2,  Culs  de  sac  like  the  finger  of  a  glove,  filled  witli 
arge  granular  globules  (cells  of  peptic  secretion),  the  fragments  of  which  are 
throAvn  upon  the  gastric  surface  by  the  excretory  tube  which  is  tilled  with  them. 
(Kolliker.) 


STOMACHAL  DIGESTION.  239 

(albuminoids).  The  salts  chiefly  found  in  it  are  phosphate 
of  soda,  and  chloride  of  sodium. 

In  order  to  study  the  properties  of  the  gastric  juice,  this 
fluid  is  procured  through  a  fistulous  opening  in  the  stomach, 
generally  of  a  dog.  Blondlot,  of  Nancy,^  was  the  first  to 
employ  this  method,  which  has  since  yielded  such  valuable 
results  in  the  hands  of  CI.  Bernard  and  Schiff. 

The  organic  (albuminoid)  matter  contained  in  the  gastric 
juice  is  a  sort  of  ferment  called  pepsm  or  gasterase:  this 
ferment  is  of  a  soluble  nature,  like  that  of  the  saliva  (ptya- 
line).  Its  existence  was  first  pointed  out  by  Schwann; 
Payen  obtained  it  by  precipitation  from  the  gastric  juice  by 
alcohol ;  in  this  way,  pure  pepsin  may  be  produced,  pre- 
senting, after  desiccation,  the  appearance  of  a  white  powder : 
it  is  often  adulterated  for  purposes  of  trade  by  being  mixed 
with  starch.  Pepsin  exhibits  all  the  reactions  of  albuminoid 
substances,  though  its  albuminoid  nature  (Brucke),  as  well  as 
that  of  ptyaline  (Cohnlieim),  has  been  denied.  (See  Ritter, 
op.  clt.).  It  acts  on  the  albuminoid  substances  of  ali- 
ments by  transforming  them  into  albuminose  or  peptone^ 
which  is  an  isomeric  form  of  albumen,  and  can  neither  be 
precipitated  by  heat  nor  by  acids,  and  is  readily  absorbed. 

The  presence  of  an  acid  is  necessary  for  this  transforma- 
tion, which  essentially  constitutes  the  digestive  function  of 
the  stomach  ;  in  the  gastric  juice  therefore  pepsin  is  united 
with  an  acid  in  a  free  state;  the  exact  nature  of  this  acid 
has  been  much  disputed,  but  it  has  been  proved  by  artificial 
digestion  that,  whatever  it  may  be,  the  effect  produced  by  it 
is  always  the  same.  Some  maintain  that  in  the  normal  gas- 
tric juice,  this  element  is  represented  by  hydrochloric  acid 
(Prout,  Schmidt,  Mulder,  Brinton,  Rouget,  Ritter,  etc.) ; 
others,  by  phosphoric  acid  (acid  phosj)hate  of  lime,  Blond- 
lot)  ;  and  others  still,  by  lactic  acid  (CI.  Bernard,  Barres- 
will)  :  the  latter  opinion  is  now  most  generally  held. 

It  must  be  admitted  that  the  arguments  which  have 
decided  physiologists  in  favor  of  the  existence  of  different 
acids  have  all  some  foundation,  but  may  all  be  more  or  less 
completely  refuted,  and  that  organic  chemistry  seems,  up  to 

especially  about  the  region  of  the  pylorus.  Sappey  has,  however, 
shown  that  these  supposed  closed  follicles  are  only  tubular  glands, 
of  which  the  excretory  canal  is  obliterated,  and  which  develop  in 
the  form  of  a  small  spherical  cyst.  (See  "  Anat.  Descriptive," 
Vol.  IV.,  p.  18r.) 

1  Blondlot,  "  Traite  Analytique  de  la  Digestion."     1843. 


240  DIGESTIVE  SYSTEM. 

this  time,  to  be  powerless  to  dispel  all  doubts  on  the  subject. 
Blondlot's  acid  phosphate  of  lime  appears  really  to  exist  in 
the  gastric  juice,  that  is  in  the  gastric  juice  of  dogs  that  have 
been  fed  on  bones ;  it  is  thus  only  the  remains  of  former 
digestion.  The  same  objection  may  be  made  in  regard  to 
lactic  acid:  indeed  if  lactate  of  zinc  be  obtained  by  the  action 
of  the  gastric  juice  upon  that  metal,  the  lactic  acid  which  is 
then  observed  is'often,  perhaps,  only  the  remains  of  previous 
digestion.  On  the  other  hand,  it  is  quite  possible  that 
hydrochloric  acid,  the  presence  of  which  is  incontestably 
proved  by  chemical  reactions,  may  arise  from  decomposition 
of  the  chlorides  by  the  lactates :  "  a  mixture  of  albumen  and 
chloride  of  sodium  is  coagulated  by  lactic  acid :  as  neither 
chloride  of  sodium  nor  lactic  acid  of  itself  produces  this 
effect,  the  coagulation  can  only  be  attributed  to  hydrochloric 
acid  which  is  produced  by  double  decomposition."  (Cailliot. 
These  by  Ritter).  The  best  arguments  that  can  be  adduced 
in  favor  of  the  presence  of  hydrochloric  acid  are  the  follow- 
ing: elementary  analysis  of  the  gastric  juice  reveals  more 
chlorine  than  is  requisite  to  saturate  the  soda  found  in  it: 
there  must  therefore  be  some  chlorine  in  the  form  of 
hydrochloric  acid;  so  long  as  the  chlorine  remains  in  the 
gastric  juice,  the  soda  of  the  chloride  of  sodium  remains  in 
the  blood,  whence  the  increase  of  alkalinity  in  the  blood,  and 
to  such  a  degree  that  the  urine,  which  in  its  normal  condition 
is  acid,  becomes  alkaline  during  energetic  digestion  (Brinton, 
Bence  Jones).  On  the  other  hand,  Schiff  has  shown  that 
the  introduction  of  dissolved  dextrine,  by  the  veins  or  the 
rectum,  promotes  digestion  by  the  stomach,  the  acidity  of 
the  gastric  juice  being  increased.  If  this  fact  be  true,  the 
acid  thus  obtained  in  a  larger  quantity  can  only  be  the  lactic 
acid. 

The  flavor  and  the  acid  reaction  of  the  gastric  juice  have, 
however,  been  greatly  exaggerated :  in  pathological  cases 
this  acidity  increases ;  but  in  the  normal  condition  it  is  so 
slight  as  not  to  be  sensible  to  the  taste.  The  acid  smell  of 
the  substances  thrown  off  by  the  stomach  arises  from  decom- 
position of  its  contents :  indeed,  under  certain  circumstances, 
fatty  volatile  acids  may  be  formed  in  it  (butyric  acid). 
These  properties  show  that  the  gastric  juice  does  not  consti- 
tute a  mucous  or  a  glairy  acid,  as  was  supposed,  but  a  peculiar 
fluid  analogous  to  and  comparable  with  the  saliva. 

In  order  to  complete  the  subject  of  the  products  given  off 
in  the  stomach,  we  must  add  that  this  organ,  as  well  as  the 


STOMACHAL  DIGESTION.  241 

rest  of  the  intestinal  tube,  produces  gases  in  considerable 
quantity;  chiefly  carbonic  acid  and  nitrogen.  Thus  these 
do  not  always  arise  from  fermentation  but  really  come  from 
the  blood,  and  are  evolved,  for  instance  in  all  cases  of  para- 
lysis of  the  digestive  tube,  whether  or  not  it  contains  ali- 
mentary substances;  they  may  thus  be  suddenly  produced 
under  the  influence  of  moral  emotions,  and  be  as  quickly 
reabsorbed. 

CI.  Benard  has  recently  called  the  attention  of  physiolo- 
gists to  similar  facts.  "  In  the  lung,"  he  says,  "  and  on  the 
cutaneous  surfacje,  these  gases  may  be  exhaled  simply  as  a 
result  of  simple  interchange  between  the  exterior  and  the 
interior  medium;  but  in  the  intestine,  in  which  normally  no 
air  exists,  the  exhalation  of  gas  must  take  place  by  means  of  a 
diflerent  mechanism.  The  nervous  system  has,  probably,  some 
influence  in  producing  these  gases,  for  I  have  known  them 
to  appear  in  large  quantities  after  operations  performed  upon 
the  spinal  cord.  The  eliminated  gaseous  substances  are 
generally  those  which  can  be  absorbed.  Hydrogen,  how- 
ever, which  is  not  sensibly  absorbed,  is  sometimes  exhaled 
in  various  quantities,  as  shown  in  experiments  by  Regnault 
and  Reiset."^ 

The  conditions  under  which  the  fluids  of  the  stomach  are 
secreted  are  quite  peculiar.  Thus  mucus  is  readily  pro- 
duced when  the  stomach  is  fisting  or  fatigued,  or  when 
occupied  by  a  foreign  body  which  is  not  alimentary ;  a 
sponge,  introduced  into  the  stomach,  imbibes  a  mucus 
which  is  sometimes  strongly  acid  (gastric  juice  without  pep- 
sin) and  must  not  be  confounded  with  the  real  gastric  juice, 
as  was  fomierly  done. 

The  real  gastric  juice  is  secreted  only  under  the  influence 
of  an  excitant  of  a  peculiar  character,  an  alimentary  sub- 
stance ;  or,  in  other  words,  secretion  takes  place  chiefly  when 
the  aliment  is  an  albuminoid  (muscular  flesh,  fibrine,  white 
of  ^gg)-,  that  is  to  say  an  aliment  which  essentially  requires 
tlie  action  of  the  gastric  juice.  Under  these  circumstances 
the  coat  of  the  stomach  in  all  those  parts  which  come  in 
contact  with  a  suitable  excitant,  becomes  red  and  turgescent, 
and  there  ensues  an  abundant  secretion  of  the  gastric  juice, 
which  soon  transforms  the  albuminoid  aliment  into  albunii- 
nose.    These  facts  show  that  the  secretion  of  the  gastric 

1  CI.  Benard,  "  De  la  Physiologie  G6n6rale."  Notes,  p.  290, 
1872. 

16 


242  DIGESTIVE  SYSTEM. 

juice  is  the  result  of  a  special  sensibility  on  the  part  of  the 
mucous  of  the  stomach,  and  that  this  delicate  sensibility  can- 
riot  be  deceived :  an  aliment  suitable  to  digestion  by  means 
of  the  gastric  juice  is  needed  to  produce  it.  The  mucus,  on 
the  contrary,  is  secreted  when  the  stomach  craves  food,  or  is 
occupied  by  a  foreign  body,  which  the  mucus  surrounds  and 
isolates. 

It  has  also  been  ascertained  that  after  section  of  the 
pneumogastric  nerves,  the  gastric  juice  is  still  formed, 
though  in  smaller  quantity:  the  nerves  are  not,  therefore, 
indispensable  to  the  act  of  digestion ;  the  great  sympathetic 
nerve  is  generally  considered  as  regulating  the  digestion  of 
the  stomach. 

That  remarkable  peculiarity  by  which  the  secretory  organs 
of  the  stomach  yield  genuine  gastric  juice  only  when  in 
contact  with  certain  alimentary  substances,  is  now  fully 
recognized,  but  ought  not,  perhaps,  to  be  attributed  to  a 
peculiar  sensibility^  to  a  sort  of  intuition  (Blondlot)  of  the 
stomach ;  but  rather,  according  to  Lucien  Corvisart  and 
Schiff,  to  the  fict  that  these  substances  furnish  an  indispen- 
sable element  in  the  secretion  of  pepsin :  this  is  the  theory 
of  the  peptogenous  substances  and  peptogeny  of  Schiff,  a 
theory  which  has  already  produced  many  practical  results, 
and  which  we  will  here  sketch  ra{)idly. 

Schiff  has  proved  by  numerous  experiments  that  pepsin 
is  not  formed  uninterruptedly  in  the  peptic  glands,  simply  by 
the  nutrition  of  the  coats  of  the  stomach ;  but  that  a  stomach 
fasting  and  exhausted  by  copious  digestion  loses  the  prop- 
erty of  yielding  a  gastric  juice  which  is  really  active,  until, 
having  absorbed  certain  substances,  the  coats  of  the  stomach 
become  ladened  with  elements  which  are  capable  of  being 
changed  into  pepsin :  these  substances  are  called  peptogens. 
Thus,  after  the  exhaustion  produced  by  copious  digestion 
continuing  from  twelve  to  twenty-four  hours,  the  empty 
stomach  nearly  loses  its  power  of  digesting  the  albumen; 
but  this  power  increases  in  a  remarkable  degree,  if  a  moder- 
ate quantity  of  other  aliments  {peptogens)  be  introduced 
into  it  along  with  the  albumen.  In  this  case,  the  stomach 
first  secretes  a  purely  acid  fltiid,  which  serves  to  dissolve  the 
peptogenous  elements ;  and  as  these  become  absorbed,  and, 
mixing  with  the  blood,  enable  it  to  furnish  pej)sin  to  the  glands 
of  the  stomach,  we  observe  that  the  secretion  of  a  gastric 
juice  becomes  constantly  more  active  or,  in  short,  peptic. 
These  peptogens  are  essentially  represented  by  the  elements 


STOMACHAL  DIGESTION.  243 

of  meat  which  are  soluble  in  water,  by  gelatine  and  by  dex- 
trine: broth  and  soup  thus  contain  a  large  quantity  of 
peptogenous  matter,  and  our  every  day  experience  in  this 
respect  agrees  perfectly  with  the  latest  scientific  data. 

These  peptogens  appear  to  be  absorbed  by  the  stomach, 
but  their  action  would  be  precisely  the  same,  if  they  were 
introduced  into  the  organism  by  being  injected  into  the  sub- 
cutaneous cellular  tissue,  into  the  rectum,  or  directly  into 
the  veins.  It  is  remarkable  that  when  absorbed  by  the  small 
intestine,  these  peptogens  entirely  lose  their  power ;  not  be- 
cause of  any  change  produced  in  them  by  the  intestinal 
canal,  by  the  bile  or  the  pancreatic  juice;  but  because,  being 
absorbed  by  the  chyle  ducts,  they  cease  to  be  peptogens,  in 
passing  through  the  mesenteric  glands.  It  must  be  admitted 
that  Schiif' s  researches  on  this  latter  point  have  not  the  pre- 
cision which  marks  the  earlier  part  of  his  series  of  investiga- 
tions; and  that  it  is  hardly  possible  to  believe  all  the 
experiments  the  aim  of  which  is  to  show  the  action  of  the 
mesenteric  ganglions ;  but  the  question  of  absorption  by 
the  stomach  and  of  the  uselessness  of  intestinal  absorption, 
does  not,  in  spite  of  the  apparent  paradox,  at  all  diminish  the 
general  importance  of  the  theory  of  peptogeny,  as  a  question 
of  pure  physiology,  and  as  the  fruitful  source  of  therapeutical 
applications. 

It  was,  indeed,  to  be  supposed,  a  priori^  that,  in  many 
genuine  cases  of  dyspej)sia,  that  is,  sluggishness  of  the  diges- 
tive organs;  occasioned  by  insufficiency  of  the  gastric  juice 
secreted  by  the  stomach,  the  derangement  might  be  simply 
owing  to  the  peptic  glands  not  finding  in  the  blood  the 
materials  necessary  to  impregnate  them  sufficiently.  What 
this  disease  requires,  therefore,  is  simply  an  artificial  increase 
of  the  peptogenous  substance  contained  in  the  blood,  and  it 
is  simply  necessary,  as  in  physiological  experiments,  to  pre- 
pare  the  stomach,  by  impregnating  it  beforehand  with  a 
sufficient  quantity  of  peptogens  and,  consequently,  of  pej)sin, 
in  order  that  the  work  of  digestion  may  begin  as  soon  as  food 
is  received.  Schiff  mentions  the  case  of  some  persons  suffer- 
ing from  this  malady,  who  were  cured  in  a  few  days  by 
taking  soup  an  hour  or  two  before  a  meal,  or  a  draught  of  a 
solution  of  dextrine,  or  even  an  injection  of  the  same,  half- 
an-hour  or  an  hour  before  taking  food. 

We  know  that  food  consists'  of  albuminoid  substances,  of 
feculent  or  saccharine  substances,  and,  finally,  of  fatty  mat- 
ters.   The  gastric  juice  is  not  known  to  have  any  effect  upon 


244  DIGESTIVE   SYSTEM. 

these  fatty  matters.  The  amylaceous  substances  are  changed 
into  dextrine,  and  saccharized  in  the  stomach,  by  means  of 
the  saliva  which  is  swallowed  with  the  food.  The  quantity 
of  saliva  varies  according  to  the  continuation  of  mastication 
a  longer  or  a  shorter  time :  thus  when  the  digestion  is  im- 
peded, a  larger  or  smaller  quantity  of  saliva  is  finally  swal- 
lowed, and  this  assists  the  action  of  that  which  was  swallowed 
with  the  food.  This  helps  us  to  understand  the  difficulty, 
in  artificial  digestion,  of  operating  upon  the  gastric  juice 
alone,  or  unmixed  with  saliva. 

The  albuminoid  substances,  finally,  belong  essentially  to 
the  province  of  the  gastric  juice,  and  to  that  alone  (we  are 
not  now  speaking  of  the  intestinal  juices).  If  a  piece  of 
muscular  flesh  be  placed  in  contact  with  the  saliva,  it  quickly 
putrefies ;  while  if  the  same  experiment  be  made  with  the 
gastric  juice,  the  meat  is  preserved,  and  even  putrefaction, 
which  has  already  begun,  arrested.  The  saliva  thus  evi- 
dently has  no  effect  upon  this  class  of  aliments.  The  prop- 
erty possessed  by  the  gastric  juice  of  arresting  decomposition 
was  first  observed  by  Spallanzani,  and  several  surgeons  have 
attempted  to  make  use  of  it,  in  arresting  the  putrefaction  of 
wounds.  The  odor  of  the  stomach  of  those  animals  which 
feed  on  carrion  is  not  more  powerful  than  that  of  others, 
even  after  the  ingestion  of  meat  which  is  very  strongly 
tainted. 

The  most  remarkable  effect  produced  on  albuminoid  sub- 
stances by  the  gastric  juice  is  the  transformation  which  they 
undergo.  Those  which  are  fluid  are  changed  into  another 
fluid,  more  absorbable,  and  which  does  not  coagulate  under 
ordinary  reactions.  Thus  the  white  of  Q^g^  when  mixed 
with  the  gastric  juice,  becomes  fluid  like  water.  Casein 
alone,  when  brought  into  contact  with  the  gastric  juice,  coag- 
ulates before  disappearing;  this  property  is  made  use  of  in 
curdling  milk,  by  means  of  the  pepsin  contained  in  the  pre- 
served stomach  of  a  c,^\?  {reniiet). 

The  solid  albuminoid  substances,  either  before  ingestion, 
or  when  coagulated  by  pepsin,  like  casein,  are  liquefied  by 
the  gastric  juice.  To  this  process  there  are  two  stages. 
The  albuminoid  substance,  a  small  cube  of  the  white  of  aggy 
for  instance,  first  swells ;  its  edges  then  lose  their  regular 
outline,  and  it  is  finally  reduced  to  a  tenuous  powder :  in  the 
first  stage,  no  i)art  is  really  dissolved ;  such  porphyratioh 
or  crumbling  occurs  as  would  be  produced  by  mechanical 
action,  and  yet  it  is  simply  owing  to  the  action  of  the  gastric 


STOMACHAL  DIGESTION,  245 

juice.  The  paste  thus  obtained  is  not  the  final  product  ot 
digestion  ;  it  is  what  was  formerly  called  chyme^  before  the 
action  of  the  gastric  juice  had  been  so  minutely  studied  as 
at  present.  This  first  stage  is,  however,  followed  by  a 
second,  in  which  this  pulp  becomes  completely  liquefied;  and 
it  is  under  this  form  only  that  the  products  of  digestion  pass 
from  the  stomach  into  the  intestine. 

This  porphyration  and  succeeding  liquefaction  are  accom- 
panied by  changes  of  color  in  the  digested  substances :  thus 
the  white  of  the  albumen  of  an  egg  becomes  slightly  yellow 
or  even  red;  during  the  first  stage  blood  becomes  quite 
black  (vomiting  of  half-digested  blood,  in  hemorrhage  of  the 
stomach  :'  black  hsematemesis) ;  it  is  afterwards  resolved  into 
a  nearly  colorless  fluid.  The  final  product  of  digestion  by 
the  stomach  is  usually  slightly  yellowish.  These  changes  in 
color  should  be  well  known  in  order  to  avoid  mistakes  as  to 
the  nature  of  the  substances  vomited. 

The  final  result  of  these  different  processes  is  the  produc- 
tion of  new  kinds  of  albumen,  peptones  or  alhuminoses^ 
which  are,  as  we  have  said,  especially  suited  for  absorption. 
The  peptones  always  preserve  some  feature  of  their  original 
substance :  we  can  distinguish  white  of  ^^^  from  that  of 
gelatine,  fibrine,  etc.  The  length  of  time  necessary  for  this 
transformation  depends  on  the  nature  of  the  aliments:  thus 
the  white  of  ^^^  is  digested  sooner  when  raw  than  when 
cooked ;  raw,  or  at  least  partially  cooked,  meat,  is  generally 
much  the  easiest  to  digest,  and  should  therefore  be  preferred 
(setting  aside  the  question  of  the  entozoa). 

The  study  of  the  peptones  or  albuminoses  is  one  of  those 
which  have  made  the  most  progress  of  late  years,  owing  to 
the  researches  of  Lehmann,  Brucke,  Meissner,  Mulder,  Sciiifi^, 
etc.  It  has  been  discovered,  in  the  first  place,  that  the 
perfect  peptone  is  a  remarkably  assimilable  and  endosmotic 
product :  its  chief  characteristic  in  a  physiological  point  of 
view  is,  that,  if  it  be  injected  directly  into  the  veins,  it  does 
not  reappear  in  the  urine,  slwwing  that  it  is  immediately 
assimilated  by  the  tissues.  Chemically  considered,  it  can  be 
precipitated  neither  by  heat,  acids,  nor  alkalies,  but  solely  by 
bichloride  of  mercury,  Millon's  reagent  (nitrous  or  acid 
nitrate  of  mercury)  and  some  other  rare  reagents.  The  real 
peptone  thus  consists  of  albumen  which  is  not  only  dissolved^ 
but  also  transformed  (chiefly  by  hydration,  according  to 
Brinton). 

The  real  definite  peptone  is  not,  however,  produced  in  the 


246  DIGESTIVE  SYSTEM. 

first  place  by  the  action  of  the  gastric  juice ;  in  the  series  of 
processes  which  we  have  described  (breaking  down,  liquefac- 
tion, change  of  color),  a  series  of  decompositions  occur,  pro- 
ducing tolerably  well-defined  intermediate  peptones ;  such  as 
the  dyspeptone,  the  parapeptone,  the  metapeptone,  and, 
finally,  the  definite  peptone. 

The  dyspeptone  is  the  residuum  of  digestion  of  the  casein ; 
it  is  quite  insoluble,  and  cannot  be  assimilated.  The  charac- 
teristic of  the  parapeptone  is  that  it  is  precipitated  by  neu- 
tralizing its  acid  solution;  the  metapeptone,  on  the  contrary, 
is  precipitated  by  increasing  the  acidity  of  the  product  of 
the  stomach,  and  definitively  by  concentrated  mineral  acids. 
These  forms  are  only  transitory,  and  as  the  digestion  ap- 
proaches its  termination,  they  have  all  a  tendency  to  change 
into  genuine  peptones,  with  the  exception  of  the  dyspep- 
tone which  remains  in  its  former  state,  and  of  the  parapep- 
tone, which  shows  a  tendency  to  change  into  the  same. 
Some  less  important  forms  of  transition  have  been  observed 
between  the  metapeptone  and  the  definite  peptone  (peptone 
A,  peptone  B),  which  are  principally  produced  during  the 
digestion  of  the  fibrine  (Meissner,  De  Bary,  Thiry). 

These  transformations,  especially  the  definite  peptone,  are 
owing  t6  the  combined  influence  of  the  acid  and  the  pepsin 
of  the  gastric  juice:  these  two  elements  of  the  digestive 
fluid  must  act  together.  For  instance,  it  would  be  useless  to 
operate  on  meat  with  hydrochloric  acid,  and  then,  after  com- 
plete washing,  to  place  it  under  the  influence  of  a  solution 
of  pepsin :  in  this  case  no  peptones  would  be  formed ;  the 
albumen  only  would  be  more  or  less  entirely  dissolved.  On 
the  other  hand,  if  pepsin  and  any  acid  (x^Vtt  ^o  y^^  in 
solution)  be  employed  simultaneously,  we  can  produce  in 
vitro  artificial  digestion,  yielding  nearly  the  same  results  as 
natural  digestion. 

The  production  of  the  real  peptones  must  not  be  supposed, 
however,  to  be  one  of  those  processes  of  transformation  to 
which  the  organism  alone,  or  some  growtb  (pepsin)  bor- 
rowed from  the  organism,  can  give  rise.  This  transforma- 
tion, like  all  the  chemical  transformations  which  we  see 
taking  place  in  plants  and  in  animals,  shows  no  such  mono- 
poly of  power  as  theorists  of  all  ages  have  agreed  in  attrib- 
uting to  the  agents  of  life.  Peptones  may  be  artificially 
produced,  but  the  process  is  long,  and  more  curious  than 
practical.  Meissner  obtained  perfect  peptones  from  muscu- 
lar flesh,  with  casein,  legumin,  etc.  {alhuminose  by  boiling. 


STOMACHAL  DIGESTION.  247 

E.  Corvisart),  by  long  decoction  in  Papin*s  digester;  the 
game  process  with  white  of  egg  yields  raetapeptone,  which 
may  be  afterwards  transformed  by  the  stomach  or  by  artifi- 
cial gastric  juice  into  genuine  peptones.  Peptones  have  also 
been  produced  by  the  action  of  ozone  on  the  albumen  of  an 
eg^  and  on  casein  (Gorup-Besanez,  Schiff),  but  for  this 
puipose  the  ozonized  air  must  be  made  to  pass  during  six- 
teen to  twenty  days  through  a  solution  of  albumen  and 
water;  and  this  process,  after  all,  yields  only  products  resem- 
bling peptones;  if  injected  into  the  veins  of  an  animal,  some 
of  them  will  reappear  in  the  urine  (Schiff).^ 

If  we  study  the  phenomenon  of  gastric  digestion  as  a 
whole,  we  no  longer  find  in  it,  element  by  element,  the  simple 
action  which  we  have  been  examining:  we  know  that  the 
amylaceous  substances  continue  to  be  transformed  into  sugar 
by  the  action  of  the  saliva.  The  fats  become  slightly  emul- 
sive under  the  influence  of  the  motions  of  the  stomach, 
and  by  mingling  with  the  crumbled  product  of  the  solid 
albuminoids ;  but  this  emulsion  is  extremely  unstable,  and  the 
drops  of  fat  show  a  tendency  to  reunite  in  large  masses, 
which  float  on  the  surface  of  the  liquid.  The  different 
albumens  are  transformed  into  different  peptones^  but  there 
are  some  kinds  which  for  a  long  time  resist  the  action  of  the 
gastric  juice  :  such  as  the  cellular  tissue  of  the  muscles:  and 
some,  finally,  as  the  celluk)se  of  plants,  whicli  are  almost 
refractory.  The  mingling  of  these  different  substances  with 
a  large  quantity  of  gastric  juice  forms  what  has  also  been 
called  chyme.  But  we  see  here,  too,  that  the  chyme  is  not  a 
substance  immediately  formed,  but  an  extremely  complex 
pulp,  and  not  at  all  fitted  to  give  an  exact  idea  of  the  diges- 
tive action  of  the  stomach. 

Attempts  have  been  made  to  decide  on  the  quantity  of 
gastric  juice  necessary  to  dissolve  an  aliment.  In  artificial 
digestion  a  large  quantity  is  required :  thus  one  part  of  con- 
crete albumen  requires  twenty-five  parts  of  the  juice ;  the 
quantity  secreted  is,  therefore,  very  abundant,  and  is  esti- 
mated by  litres:  in  man,  for  instance,  it  may  be  twenty  litres 
in  tvventy-four  hours.  The  usual  standard  in  animals  is  one 
hundred  grammes  of  gastric  juice  to  one  kilogramme  of  the 

*  See  CI.  Bernard,  "  Lemons  sur  les  Proprietes  Physiologiques 
et  les  Alterations  Pathologiques  des  Liquides  de  I'Organisme." 
Paris,  1859. 

Blondlot,  "  De  la  Mani^re  d'agir  du  sue  Gastrique."  (Gazette 
Medicale,  1857.) 


248  DIGESTIVE  SYSTEM. 

animal's  weight :  this  would  give  for  man,  whose  mean  weight 
is  sixty-five  kilogrammes,  only  6500  grammes  of  gastric  juice 
(in  twenty-four  hours). 

The  most  moderate  estimate  thus  places  the  weight  of  this 
juice  at  one-tenth  of  that  of  the  body  of  the  animal  during 
the  period  of  twenty-four  hours.  The  case  has  even  been 
cited  of  a  woman,  having  a  gastric  fistula,  and  was  nursing, 
who  yet  at  the  same  time  produced  a  quantity  of  gastric 
juice  equal  in  weight  to  one  quarter  of  that  of  her  body 
(Bechamp). 

B.  Small  intestine. 

Intestinal  Secretions  and  Digestion.  —  We  are  already 
acquainted  with  the  epithelium  of  the  intestinal  tube, 
properly  so  called,  its  villosities  and  its  glands  (p.  191). 
We  will  study  the  villosities  more  completely  when  we 
come  to  the  subject  of  absorption.  What  we  have  to  do 
now  is  to  seek  to  discover  the  nature  of  the  fluids  which 
flow  from  the  glands,  and  which  come  more  or  less  in  contact 
with  the  product  of  the  digestion  of  the  stomach. 

The  contents  of  the  stomach  enter  the  intestine  in  waves, 
and  pass  very  quickly  through  the  first  part  of  the  tube;  this 
tube  has  been  called  the  jejunum.,  because  it  is  generally 
found  empty,  the  contents  of  the  intestine  accumulating  in 
the  lower  part  of  the  small  intestine  {ileum).  It  has  been 
generally  supposed  that  the  secreted  products  of  the  differ- 
ent glands  were  poured  into  the  intestine  at  this  moment, 
and  thus  came  in  contact  with  the  alimentary  substances. 
This  is  the  case  with  regard  to  the  product  of  the  glands  of 
Lieberkiihn,  and  that  of  the  pancreas,  but  not  of  the  bile. 
Study  of  biliary  fistul83  proves  that  the  bile  is  poured  into 
the  intestine  long  after  the  passage  of  the  product  of  the 
stomach.  The  secretion  of  the  bile  is  connected  with  absorp- 
tion, not  digestion,  and  we  will  study  it  under  that  head. 

The  fluid  secreted  by  the  glands  of  Lieberkiihn  constitutes 
the  enteric  juice:  this  juice  is  very  difficult  to  collect,  and, 
on  this  account,  the  ideas  entertained  respecting  it  were 
erroneous,  or,  at  least,  extremely  hypothetical :  Thiry's  pro- 
cess of  procuring  it,  which  is  now  employed,  consists  in 
isolating  a  certain  length  of  the  intestinal  tube  by  two  sec- 
tions ;  and  joining  the  tube  together  again,  so  that  the  fluids 
may  flow  as  before ;  one  extremity  of  the  part  which  has 
been  detached,  and  which  adheres  only  by  its  mesentery,  is 
then  sewed  up,  so  as  to  form  a  pocket  or  cul-de-sac,  while 


SMALL  INTESTINE.  249 

the  other  is  left  open,  and  fastened  into  the  open  wound  in 
the  abdomen.  The  intestinal  fluid  obtained  through  this 
orifice  is  quite  pure ;  it  is  a  limpid  juice,  slightly  yellow,  very 
tenuous,  and  alkaline ;  its  properties  are  nearly  all  negative : 
it  acts  neither  on  starch  nor  on  the  fats,  nor  yet  on  the 
albumens  in  general,  but  solely  on  the  Jibrine  of  the  blood, 
which  it  changes  into  peptone.  Almost  the  only  purpose 
which  it  serves  is  thus  to  dilute  the  contents  of  the  intestine.^ 
The  secretion  of  this  fluid  takes  place  by  means  of  chemical, 
especially  acids,  or  mechanical  excitants,  such  as  the  pres- 
ence of  a  foreign  body.  In  some  pathological  cases  it  is 
secreted  in  great  abundance,  producing  the  serous  diarrhoea 
which  is  sometimes  so  alarming. 

Daily  observation  has  long  shown  what  is  the  influence  of 
the  nervous  system  in  producing  the  flow  of  the  intestinal 
fluids.  The  effect  produced  on  the  action  of  the  intestinal 
tube  by  certain  moral  impressions,  and  the  untoward  increase 
of  the  fluid  products,  which  sometimes  accompanies  a  strong 
sensation  of  fear  or  of  danger,  is  a  familiar  occurrence. 
Direct  experiments  on  animals  have  shown  that  this  is  caused 
by  reflex  paralysis  of  the  nerves  of  the  intestine,  particularly 
the  vaso-motor  nerves.  If  two  ligatures  be  placed  around  the 
intestine  at  some  distance  from  each  other,  and  the  nerves 
leading  to  the  part  included  between  them  be  cut,  the  veins 
and  arteries  being  carefully  avoided  ;  and  if  then  the  intestine 
be  replaced,  this  intestinal  loop  will  be  found  on  the  follow- 
ing day  distended  by  a  considerable  quantity  of  clear,  alkaline, 
and  very  thin  fluid,  strongly  resembling  the  enteric  juice. 
An  additional  proof  of  the  influence  of  the  nerves  consists  in 
enclosing  another  intestinal  loop  between  two  ligatures,  avoid- 
ing, however,  the  nerve  threads.  The  mucous  of  this  part  of  the 
intestine,  instead  of  being  saturated  with  fluid,  is  found  sticky 
to  the  touch,  and  nearly  dry,  as  in  an  intestine  during  fasting.^ 

The  pancreatic  juice  is  also  called  the  abdominal  salica ; 
as  the  structure  of  the  pancreas  resembles  that  of  the  salivary 
glands,  so  its  secreted  product  closely  resembles  the  saliva  ; 
it  differs  from  it,  however,  in  the  proportion  of  solid  matter, 
for  it  contains  only  90  per  cent  of  water,  while  the  saliva 
contains   99   per   cent.     The  pancreatic  juice  is,  therefore, 

^  FtcZe  Boylston  Prize  Essay,  "  On  Intestinal  Digestion,"  by  G. 
M.  Garland.     D.  Clapp  &  Son,  Boston. 

^  A.  Moreau,  "  llecherches  sur  la  Secretion  Intestinale." 
(Comptes-rendus  de  la  Socicte  de  Biologie,  18G0.) 


250  DIGESTIVE  SYSTEM, 

comparatively,  very  thick ;  it  coagulates  readily,  being  rich 
in  albumen.^  It  is  alkaline,  like  all  salivas,  and,  when 
brought  in  contact  with  the  product  of  the  stomach,  im- 
pregnated with  the  gastric  juice,  it  neutralizes  the  acidity  of 
the  latter,  and  begins  to  act  in  its  turn.  By  means  of  the 
ferments  which  it  contains,  it  acts  simultaneously  on  the 
amylaceous  substances  and  the  albuminoids:  transforming 
the  former  into  sugar,  by  the  saliva,  and  the  latter  into  pep- 
tone, by  the  gastric  juice.  This  latter  effect  is  different  from 
that  produced  by  the  pepsin,  inasmuch  as  in  this  case  lique- 
faction takes  place  instantly,  without  the  intermediate  stage 
of  porphyration.  This  juice  is  also  allowed  to  possess  the 
property  of  making  an  emulsion  of  the  fats  (CI.  Bernard), 
even  separating  some  of  them  into  glycerine  and  fatty  acids; 
but  the  latter  of  these  two  effects  appears  to  be  produced 
only  when  the  pancreatic  juice  is  decomposed,  and  the  former 
only  when  the  fat  and  pancreatic  juice  are  closely  mingled 
together  by  violent  agitation :  as  these  conditions  are  not 
realized  in  the  intestine,  we  must  conclude  that  the  pancre- 
atic juice  has  no  ])hysiological  effect  upon  the  fats ;  it  may  also 
be  directly  ascertained  by  opening  the  body  of  an  animal 
while  the  process  of  digestion  is  going  on,  that  the  fats  are 
not  in  a  state  of  emulsion,  but  aj-e  found  in  masses  in  the  in- 


'  The  identity  of  the  pancreas  and  the  salivary  glands,  even  in 
an  anatomical  point  of  view,  is  denied  by  Giannuzi,  whose  recent 
researches  have  led  him  to  consider  the  pancreas  as  rather  resem- 
bling the  liver.  "  The  excretory  tubes  of  the  pancreas  have  very 
thin  walls,  lined  inside  with  a  columnar  epithelium.  They  have 
not  the  same  connections  with  the  secretory  vesicles  as  the  salivary 
glands;  but  they  foi-m  around  them  a  net  composed  of  very  line 
tubes,  which  have  no  epitheUum,  and  surround  the  pancreatic  cells 
with  their  meshes.  This  net  may  be  compared  to  that  of  the  bil- 
iary ducts.  The  network  of  the  excretory  tubes  of  the  different 
vesicles,  which  form  the  same  glandular  lobule,  have  connections 
between  them,  and  form  a  common  network.  The  pancreatic 
vesicles  have  no  coat.  The  pavement  epithelium  of  the  vesicles  is 
formed  of  flattened  cells,  having  a  nucleus  and  a  prolongation. 
In  short,  they  are  very  similar  to  those  of  the  salivary  glands  ; 
their  nucleus,  however,  is  more  easily  perceived,  and  their  proto- 
plasm is  more  granular,  and  contains  fatty  granulations.  The 
semilunar  bodies  in  the  sub-maxillary  glands,  described  by  Gian- 
nuzi, and  since  discovered  by  Kolliker,  Ileidenhain,  and  13oll,  in 
the  saUvary  glands,  are  not  found  in  the  glandular  vesicles."  (See 
p.  2J1,  Giaunuzi,  "  Comptes-rendus  de  i'Acade'mie  des  Sci- 
ences.") 


SMALL  INTESTINE.  251 

testine.  We  shall  also  see  that  this  emulsion  is  not  necessary 
in  order  to  comprehend  the  mechanism  of  absorption. 

The  secretion  of  the  pancreas  appears  to  be  nearly  con- 
tinuous, like  that  of  the  saliva;  it  is  generally,  however,  very 
inconsiderable,  but  greatly  increases  as  the  i)roduct  of  the 
stomach  enters  the  intestine.  This  is  evidently  a  reflex  act, 
though  the  nervous  organs  of  this  phenomenon  are  not  y€t 
perfectly  known;  it  has,  however,  been  observed  that  section 
of  the  pneumogastric  nerves  checks  the  secretion  from  the 
pancreas.  When  normally  secreted,  remains  of  the  cells  of 
glandular  pouches  are  found  in  this  product :  according  to  the 
general  law,  therefore,  this  secretion  is  produced  by  the  shed- 
ding of  the  glandular  elements.^ 

The  influences  which  govern  the  secretion  of  the  pancre- 
atic fluid  appear  to  be  of  the  same  nature  as  those  which 
govern  the  secretion  of  the  gastric  juice,  and  especially  of 
the  pepsin  of  that  juice.  As  the  stomach  needs  the  pepto- 
gens  (see  p.  242,  above),  so  the  pancreas  needs  the  pan- 
creatogens ;  thus  the  pancreas  secretes,  less  by  means  of  a 
reflex  nervous  mechanism,  than  because  at  a  given  moment 
it  is  impregnated  with  those  substances  which  are  fitted,  to 
give  rise  to  secretion ;  that  is,  the  blood  brings  to  it  the 
peptones  which  have  been  already  elaborated  by  the  stom- 
ach. The  theory  of  the  pancreatogens,  established  by  L. 
Corvisart,  even  precedes  that  of  the  peptogens,  and  was  the 
starting-point  of  the  latter.^  It  has  been  taken  up  again  by 
Schiff",  who  has  introduced  into  it  some  new  ideas  as  to  the 
functions  of  the  spleen  in  regard  to  digestion.  Indeed, 
while  the  stomach  receives  the  peptogens  directly  from  the 
circulation  (provided  that  the  blood  contains  any),  the  for- 
mation of  the  pancreatic  juice  requires  the  intervention  of 
the  spleen.    After  extirpation  of  the  spleen,  or  a  deep  wound 

^  "  Does  the  secretory  cell  of  animals  concentrate  or  create  the 
direct  elements  which  it  contains  ?  It  is  difficult  to  answer  this 
question.  For  instance,  I  have  observed  that  during  hibernation 
the  pancreatic  cell  in  animals  contains  no  pancreatine.  The  case 
is  the  same  with  fasting  animals;  but  directly  food  is  received  and 
digestion  begun,  these  cells  fill  with  pancreatine  and  become  active. 
It  must  be  admitted  here,  either  that  the  pancreatine  has  been 
formed  in  the  gland  by  the  nervous  influence,  or  has  been  brought 
into  it  by  the  blood."  (CI.  Bernard,  "Da  ia  Physiologic  Gene- 
rale."     Notes,  1872,  p.  281.) 

2  L.  Corvisart,  "  De  la  Fonction  Digestive  du  Pancreas  snr  les 
A-liments  Azotes."     (Gazette  Ilebdomadaire,  1860.) 


252  DIGESTIVE  SYSTEM. 

made  in  it  by  way  of  experiment,  Schiff  has  found  that  the 
pancreatic  juice,  secreted  at  the  very  moment  when  it  is 
generally  most  active,  is  entirely  deprived  of  that  ferment 
by  means  of  which  alone  it  can  act  on  the  albumens. 

A  number  of  experimental  and  clinical  results  here  present 
themselves,  in  the  midst  of  which  it  is  difficult  to  decide  on 
which  will  finally  prove  to  be  a  gain  to  physiology ;  we  will, 
however,  sum  them  up  rapidly,  in  order  to  show  how  much 
there  still  is  to  study  in  the  digestive  functions,  and  in  the 
spleen,  an  organ  which  is  still  a  mystery  in  every  respect 
(see  p.  206). 

While  injury  to  the  spleen  weakens  the  digestive  proper- 
ties of  the  pancreatic  juice,  Schiff  discovered  that  it  renders 
the  secretion  and  the  action  of  the  gastric  juice  much  more 
active:  by  taking  out  the  stomach  and  the  pancreas  of  an 
animal,  Schiff  found  that  artificial  digestion,  by  means  of  an 
infusion  of  these  tissues,  yields  three  grammes  of  digested 
albumen  for  the  stomach,  and  from  thirty  to  fifty  centi- 
grammes for  the  pancreas.  But  if  the  stomach  that  is  used 
be  taken  from  a  similar  animal  which  has  been  previously 
deprived  of  its  spleen,  the  artificial  digestion  by  means  of  the 
gastric  membrane  will  liquefy  in  an  equal  amount  of  time 
eight  grammes  of  albumen ;  while  that  of  the  pancreas  has  no 
digestive  effect  upon  the  albuminoids.  We  see,  in  the  latter 
case,  that  the  gastric  membrane  alone  digests  a  larger  quan- 
tity of  matter  than  the  stomach  and  the  pancreas  together, 
in  the  case  first  mentioned. 

According  to  Schiff,  the  increase  of  appetite  observed  in 
animals  whose  spleen  has  been  removed,  is  caused  by  this 
large  increase  of  the  digestive  action  of  the  stomach,  and  he 
thus  explains  the  case  of  a  woman  who,  after  extirpation  of 
the  spleen,  was  afflicted  with  an  enormous  appetite. 

More  curious  facts  still  lead  us  to  infer  that  as  the  pan- 
creatic juice  loses  its  influence  over  the  albuminoids,  its 
power  over  the  fatty  and  the  amylaceous  matters  becomes  still 
greater  than  before.  (Vulpian,  "  Cours  du  Museum,"  1866.) 
In  order  to  comprehend  that  there  is  nothing  unreasonable 
in  this  view,  we  must  first  call  to  mind  that  researches  by 
Kiihne,  Danileski,  Hoppe  Seyler  (Ritter,  op.  cit.),  have 
proved  that  the  pancreatine  which  is  the  active  principle  of 
the  pancreatic  juice,  is  a  mixture  of  three  individual  fer- 
ments, having  each  an  independent  action :  the  first,  precip- 
itable  by  calcined  magnesia,  acts  upon  the  fats ;  the  second, 
separated  by  precipitation  irom  a  solution  of  collodion,  is 


SMALL  INTESTINE  253 

the  ferment  of  the  albuminoid  substances,  while  the  third, 
which  resembles  ptyaline,  is  precipitated  like  this  latter  by  con- 
centrated alcohol,  and  acts  upon  the  amylaceous  substances. 
As  these  three  active  principles  can  be  isolated,  and  act  inde- 
pendently of  each  other,  it  appears,  from  what  we  have  said, 
that  the  spleen  has  influence  over  the  ferment  of  the  albu- 
minoids only,  and  that,  moreover,  the  quantity  and  tho  action 
of  the  two  other  ferments  increases  in  direct  proportion  to  the 
diminution  of  the  first.  At  least,  the  facts  related  by  Vulpian 
a])pear  to  show  this.  "  Is  there,"  he  asks,  "  any  increase  in 
the  action  of  the  pancreatic  juice  on  the  fatty  substances, 
or  are  the  results  which  I  shall  quote  from  Schiff  caused  solely 
by  the  greater  activity  of  the  gastric  digestion  ?  It  is  true 
that  Stinstra  admits  (in  a  thesis  drawn  up  under  the  direction 
of  Van  Deen)  that  there  is  a  larger  deposit  of  fat  in  all  parts 
of  the  body  in  animals  whose  spleen  has  been  removed; 
moreover,  according  to  Schmidt,  the  farmers  in  some  parts 
of  England  have  a  custom  of  extii-pating  the  spleen  of  calves, 
in  order  to  fatten  them  more  rapidly." 

II.  Movements  of  the  Intestine.  —  The  food,  having  been 
thus  modified  by  the  enteric  and  the  pancreatic  juices,  then 
passes  through  the  small  intestine  by  means  of  its  peristal- 
tic movements.^  In  the  normal  condition  these  movements 
are  always  slow  and  feeble ;  but,  if  they  become  exagger- 
ated, pains  known  as  colicky  are  produced.  These  contrac- 
tions are  reflex,  and  are  increased  chiefly  in  pathological 
cases :  thus  the  effect  of  some  purgatives  is  to  increase  these 
movements ;  this  is  the  case  with  oils  and  vegetable  matters 
generally.  Saline  purgatives,  on  the  other  hand,  act  chiefly 
by  causing  hypersecretion  of  the  glands  of  Lieberkiihn,  and 
give  rise  to  serous  diarrhoea,  without  colic.  If  the  body  of 
a  man  who  has  died  in  good  health  and  during  digestion  be 
examined,  there  will  be  found,  at  short  distances  in  the  intes- 
tinal tube,  waves  of  alimentary  matter,  associated  with  red 
patches  upon  the  mucous  coat,  which  is  colorless  between  these 
points.  This  state  of  congestion  corresponds  with  the  more 
active  secretion  that  takes  place  at  these  points ;  the  pan- 
creas also  is  highly  congested  during  secretion. 

The  alimentary  substances  seem  to  pass  rapidly  through 
the  two  upper  portions  of  the  small  intestine  {duodenum 

^  See  Legros  and  Onimus,  *'  Recherches  Expdrimentales  sur 
les  Mouvements  de  I'Intestin."  (Journal  de  I'Anat.  et  de  la 
Physiol.,  de  Ch.  llobiu.     lbU9,  No.  de  Janvier.) 


254  DIGESTIVE  SYSTEM. 

andjejunt^m)  ;  but  as  they  approach  the  ileifm  their  progress 
seems  slower,  they  begin  to  mingle  together,  and  finally  are 
found  accumulnted  at  the  lower  end  of  the  small  intestine. 
As  they  are  subjected  to  absorption  during  this  passage,  they 
may  be  said  to  move  more  slowly  in  proportion  as  their  con- 
sistency increases  and  their  quantity  diminishes. 

IV.  Absorption. 

A.  Absorption  in  general,  role  of  the  epitheliums,  function 
of  the  villosities. 

We  have  seen  that  the  stomach  absorbs  no  part  of  its  con- 
tents, and  that  the  phenomenon  o^  rejection  (re/us)  is  caused 
by  the  vitality  of  the  epithelium  which  lines  the  mucous  coat. 
In  the  intestine,  on  the  contrary,  absorption  takes  place  very 
rapidly,  and  we  shall  also  find  that  the  phenomenon  of  pas- 
sage is  solely  dependent  on  the  characteristic  vitality  of  the 
intestinal  epithelium. 

Setting  aside  the  property  of  the  epitheliums,  the  phenom- 
ena o^  absorption  may  be  generally  considered  as  phenomena 
of  diffusion.  These  are  known  to  everybody.  Most  j)eople 
have  tried  the  experiment  of  pouring  red  wine  upon  water 
contained  in  a  glass,  pouring  it  so  slowly  as  to  prevent  the 
wine  mixing  with  the  water.  The  colored  wine  is  then  seen 
to  rest  upon  the  surface  of  the  water,  the  latter  remnining 
colorless,  as  the  wine  is  lighter  than  the  water;  and  the  two 
layers  are  so  distinct  that  one  would  imagine  that  they  could 
never  mingle.  After  a  short  time,  however,  though  remain- 
ing quite  undisturbed,  the  two  fluids  mix,  and  become  homo- 
geneous ;  the  water  has  passed  into  the  wine,  or  is  diffused 
into  it.  Something  similar  takes  place  in  absorption,  looked 
at  from  a  general  point  of  view.  Indeed,  the  organism  being 
composed  of  four-filths  of  water  to  one-fifth  of  solid  matter, 
may  be  compared  to  a  sponge  soaked  in  water.  Now,  if  a 
sponge  soaked  in  water  be  placed  in  alcohol,  the  latter  will 
penetrate  the  water  in  its  turn,  intermingling  with  it;  in 
this  case  the  sponge  may  be  left  out  of  the  account,  the 
essential  feature  of  the  phenomenon  being  an  act  of  diffusion 
between  the  alcohol  and  the  water  (contained  in  the  meshes 
of  the  sponge).  The  fact  of  the  circulation  of  the  blood  is 
only  accessory.  A  frog  may  be  deprived  of  its  circulation, 
and  yet  if  one  of  its  limbs  be  dipped  into  a  solution  of  strych- 
nine, the  poison  will  be  diffused  throughout  its  whole  body, 
will  reach  the  spinal  marrow,  and  kill  it  in  the  convulsions 


ABSORPTION.  '2,00 

of  tetanus.  If  the  circulation  still  exists,  these  phenomena 
are  produced  much  more  quickly,  because  the  motion  of  the 
blood  hastens  the  diffusion  of  the  poison,  without,  however, 
being  indispensable  to  it :  circulation  is  to  absorption  what 
the  movements  in  breathing  is  to  the  diffusion  of  the  gases  or 
res]>iration. 

The  vessels  cannot  thus,  in  the  proper  sense  of  the  word, 
be  said  to  be  absorbing  organs :  it  is,  properly  speaking,  the 
fluids  of  the  tissues,  the  blood  itself,  which  absorbs.  The 
state  of  the  blood  has  thus  a  great  effect  on  the  intensity  of 
the  absorption.  If  the  blood  be  saturated  with  water,  as, 
for  instance,  after  an  injection  of  water  into  the  veins  of  an 
animal,  a  fresh  quantity  of  water  will  not  easily  penetrate. 
Absorption  is  also  very  sluggish  in  the  case  of  hydraamia ; 
and  becomes  very  active,  on  the  other  hand,  if  the  mass  of 
the  blood  be  diminished  (by  bleeding),  or  if  it  has  been 
thickened,  as,  for  instance,  by  purgatives  or  diuretics  in  the 
case  of  the  patients  already  mentioned.  Similar  experiments 
liave  been  made  in  regard  to  absorption  of  the  fats.  If  the 
blood  is  surcharged  with  fat  (the  normal  proportion  is  3  to 
1000),  the  fatty  substances  ingested  will  be  found  nearly 
entire  in  the  alvine  discharges,  and  scarcely  any  will  be 
absorbed.  We  may  therefore  say,  in  conclusion,  that  the 
state  of  saturation  or  non-saturation  of  the  blood  is  one  of 
those  causes  which  have  the  most  influence  on  absorption,  in 
regard  to  one  substance  or  another. 

This  diffusion,  however,  can  take  place  only  when  the  epi- 
thelium which  forms  the  barrier  between  the  organism  and 
the  fluids  deposited  on  its  surface  permits  and  facilitates  their 
passage :  the  chief  point  of  the  study  of  absorption  is  thus 
the  attitude  assumed  by  the  intestinal  epithelium  during 
these  phenomena. 

In  order  to  increase  its  points  of  contact  with  the  matters 
to  be  absorbed,  the  intestinal  mucous  forms  numerous  folds, 
as  the  valvulce  conniventes^  and  especially  the  villi.  These 
are  composed  of  a  casing  of  columnar  cells  (Fig.  68),  which, 
as  seen  in  front,  appear  as  a  sort  of  hexagonal  flooring  (free 
base  of  the  cell),  while  at  the  summit  they  are  inserted  in 
the  body  of  the  villus  (Fig.  69,  A),  and  are  in  contact  with 
smaller  cells,  polyhedral  or  irregular,  the  germs  of  future 
columnar  cells  (which  are  to  these  what  the  layer  of  Mal- 
pighi  is  to  the  more  superficial  cells  of  the  epidermis).  The 
central  part,  or  body  of  the  villus^  is  very  complex  (see  Fig. 
69,  A  and  C).     This  is  composed  of  an  embryonic  connective 


256  DIGESTIVE  SYSTEM. 

tissue,  having  a  large  number  of  embryonic  or  plasmatic  cells. 

In  this  tissue  are  found  two 
vascular  systems,  the  first  being 
a  network  of  blood  vessels 
placed  throughout  the  deeper 
tissues,  and  especially  near  the 
surface,  so  near  that  they  almost 
touch  the  epithelium.  The  sec- 
ond is  a  central  tube,  the  ex- 
-    ,-  ,^v  ,.      *    tremity    of   a    chyle-duct ;    it 

I  of  columnar  epithehuni  *     ^  ••'^  ^.i*^  -f. 

terminates  at  the  summit  of 
the  body  of  the  villus,  but  in  a  manner  at  the  present  time 
unknown  (see  lymphatic  system,  p.  201,  above).  Some  main- 
tain that  it  terminates  in  a  cul-de-sac,  and  others  that  it  is 
gradually  blended  with  the  substance  of  the  body  of  the 
villus  or  papilla.  However  this  may  be,  the  general  appear- 
ance would  lead  to  the  belief  that  this  tube  is  only  the 
excretory  tube  of  the  network  of  blood-vessels,  in  the  midst 
of  which  it  is  placed.  We  see  thus  that  the  blood-vessels 
are  better  fitted  for  absorption  than  the  chyliferous  vessels.^ 

When  the  stomach  pours  its  contents  into  the  small  intes- 
tine, the  villi,  both  the  epithelium  and  the  body  of  the  villus, 
change  their  appearance  as  the  fluid  passes  through.  This 
phenomenon  may  be  artificially  produced  by  taking  the  fluid 
from  a  stomach  in  which  digestion  is  going  on,  filtering  it, 
and  bringing  it  into  contact  with  the  intestinal  mucous, 
recently  taken  from  the  body  and  still  living.  Any  other 
substance  than  the  contents  of  the  stomach,  that  is,  any 
element  which  has  not  been  diluted  with  a  large  amount  of 
gastric  juice,  would  produce  no  effect  upon  the  intestinal 


1  According  to  some  recent  researches  by  Debove  ("  Compt. 
rend,  de  l' Academic  des  Sciences."  Decembre,  1872),  these  deep 
cells  form  an  endothelial  laijei\  that  is  to  say,  formed  of  cells  iden- 
tical with  those  which  cover  the  serous  membranes,  flat  cells 
joined  together  by  a  very  fine  cement :  they  are  made  visible  by 
employing  nitrate  of  silver.  What  His  saw  in  the  villi,  and  de- 
scribed as  the  casing  of  a  central  chyliferous  vessel,  would  be, 
according  to  Debove,  precisely  the  endotheUal  or  sub-epithelial 
layer  belonging  to  the  surface  of  the  villus. 

*  rj,  Four  cells  joined  together,  seen  from  the  side ;  the  free  surface  (at 
the  top)  shows  a  thick  border,  striped  with  tine  stria;,  b,  Similar  cells,  their 
disengaged  surface  being  inclined  upwards  and  outwards :  the  hexagonal  form 
of  the  section  and  the  thick  edge  should  be  remarked,  c,  Cells  modified  and 
slightly  distorted  by  imbibition,  their  upper  edge  appearing  ravelled.    ( Virchow.) 


ABSORPTION. 


257 


mucous;  but,  on  contact  with  this  fluid,  even  four  hours 
after  death,  the  mucous  becomes  white  and  thicker  and  more 
resisting.  On  examining  it  closer,  we  find  that  these  phe- 
nomena are  at  first  only  caused  by  changes  in  the  epithelium. 
The  epithelial  cells,  which,  when  the  animal  is  fasting,  are 


Fig.  69.  — Intestinal  villosities  observed  during  absorption  (especially  during 
the  absorption  of  fat).    (Virchow.)  * 

small,  somewhat  diflluent,  and  hardly  forming  a  distinct 
membrane,  swell  when  excited  by  the  gastric  juice ;  and,  as  it 
were,  standing  erect,  become  three  times  their  original  size, 
forming  a  resisting  membrane,  which  may  almost  be  dis- 
sected ;  the  villi  are  then  pressed  against  each  other,  the  epi- 
thelium forming  four-fifths  of  their  bulk.  The  epithelial  cells 
also  change  in  color,  becoming  whitish ;  this  seems  to  be  due 
to  the  large  number  of  drops  of  fat  found  inside  them,  and 
the  same  phenomenon  takes  place  even  when  the  fluid  of 
the  stomach,  which  is  brought  in  contact  with  the  mucous, 
contains  no  fat.  We  know,  however,  that  every  cell  con- 
tains fat ;  this  fat,  it  is  true,  is  disguised,  but  it  becomes  visi- 
ble under  certain  circumstances,  especially  when  an  interior 


*  A,  Intestinal  villosity  of  man,  taken  from  the  jejunum.  In  a  we  see  the 
colniunar  epithelium,  with  its  nuclei,  continuin£?  as  far  as  the  surface  of  the 
villosity.  c,  Central  chyliferous  duct,  v,  v,  Blood-vessels.  The  embryonic 
nuclei  of  the  connective  tissue  are  seen  in  the  remaining  part  of  the  hotly  of  the 
villositv. 

B,  "V'illosity  of  a  dog,  contracted. 

O,  Villosity  of  man  during  intestinal  absorption,  the  fat  becoming  a  part  of 
the  body  of  the  villus  itself.    In  D  a  large  collection  of    fat  is  seen.    (280 
■      •) 

17 


258  DIGESTIVE   SYSTEM. 

change  takes  place,  which  seems  to  be  the  signal  of  the  death 
of  the  cell.  It  therefore  appears  probiible,  that  the  columnar 
epithelium,  which  we  are  considering,  is  near  its  end,  that  it 
will  soon  fall  into  decay,  and  that  an  actual  inoulting  of  the 
epithelium  of  the  mucous  will  take  place :  this  is  what,  we 
find,  actually  occurs.  When  the  chyme  contains  fatty  mat- 
ters, this  effect  is  still  more  apparent;  the  white  is  more 
brilliant  and  the  fat  globules  larger :  but  here,  too,  the  whole 
surface  disappears,  and  a  new  epithelium  takes  its  place.^ 

This  whitish  appearance  and  turgescence  begin  at  the  free 
base  of  the  epithelium,  extending  gradually  to  its  depth,  and 
spreading  over  the  whole  villus  (Fig.  69,  C).  It  is  always, 
however,  the  epithelium  of  the  summit  of  this  papilla  which 
first  becomes  whitish  and  swollen,  thus  imparting  to  the  vil- 
lous projection  a  peculiar  appearance,  which  enables  us  to 
understand  what  Lieberkiihn  saw,  and  explained  by  giving 
it  the  name  of  ampulla  (small  aspiratory  reservoir  of  the 
chyle).  The  change  in  the  mandrel  of  the  villus  follows 
that  in  the  epithelium ;  and  as  the  latter  becomes  granular, 
and  is  about  to  fall,  the  summit  of  the  villus  appears  to  change 
into  a  cluster  of  small  drops  of  fat,  which  are  seen  first  in  the 
body,  and  then  at  the  base  of  the  villus,  and  are  often  more 
or  less  regularly  ranged  in  rows.  This  would  lead  to  the 
supposition  that  there  are  separate  vessels,  but  it  seems  more 
probable  that  phenomena  of  nutrition  are  taking  place  in  the 
plasmatic  elements  of  the  mucous,  and  that  tliey  are  accom- 
panied by  metamorphoses  similar  to  those  which  we  have 
seen  in  the  epithelium.  These  phenomena  are  still  more 
striking  when  the  intestinal  fluid  contains  a  large  quantity 
of  fiit  (Fig.  69,  C,  D). 

This  appearance  is  sometimes  modified,  especially  in  the 
dog  (Fig.  69,  B),  by  the  deformation  of  the  villus ;  but  this  is 
only  an  accessory  phenomenon,  and  is  caused  by  the  con- 
traction of  the  smooth  muscular  fibres.  The  body  of  the 
villus,  in  fact,  contains  rudimentary  contractile  elements, 
arranged,  especially  around  the  central  chyliferous  vessel, 
in  striae  longitudinal  to  the   axis   of  the  villus ;    they  are 

1  See  Kiiss,  "  Gazette  Medicale  de  Strasbourg."  181G,  p.  38, 
Sur  V absorption. 

Finck,  "  Sur  la  Physiologie  de  I'Epith^lium  Intestinal."  These 
de  Strasbourg,  1851,  No.  324. 

L.  Lereboullet,  "  De  I'Epithelium  Intestinal  an  point  de  vue  de 
r Absorption  des  Matieres  Grasses."  These  de  Strasbourg,  1866, 
No.  957. 


ABSORPTION.  259 

curved  in  an  arch,  at  the  summit,  and  here  Moldschott  and 
Donders  have  discovered  smooth  contractile  fibres  (contrac- 
tile cells)  arranged  transversely. 

This  is,  in  short,  a  phenomenon  of  passage;  the  epithelium, 
on  account  of  its  own  life  and  its  nutrition,  becomes  filled 
with  the  product  of  digestion  with  which  it  was  in  contact, 
and  conveys  this  to  the  globular  elements  of  the  body  of  the 
villus  which  it  penetrates ;  the  phenomenon  of  difihsion  is 
then  all  that  is  necessary  in  order  that  the  blood  may  absorb 
the  fluids  which  come  in  immediate  contact  with  it.  This 
phenomenon  of  passage  has  been  examined  chiefly  in  regard 
to  the  fats,  because  their  optical  properties  render  observa- 
tion easier  in  their  case,  but  the  process  is  probably  the 
same  with  the  other  elements  (albuminoses  and  glucoses), 
though  this  cannot  be  directly  ascertained :  it  is  only  by 
means  of  the  fats  that  we  can  trace  the  process  as  it  goes 
on. 

Thus  we  see  that  in  this  phenomenon  of  passage^  neither 
the  phenomena  of  capillarity  nor  of  endostnosis  are  con- 
cerned ;  all  this  takes  place  in  virtue  of  the  special  function 
of  the  epithelial  cells,  and  of  the  plasmatic  elements  of  the 
body  of  the  villus;  having  arrived  at  this  point  the  absorbed 
fluids  only  require  to  be  diff'used  in  order  to  spread  through- 
out the  organism,  by  means  of  organs  which  we  shall 
study  presently.^    The  passage  of  the  sugars  and  the  albumi- 

'  It  is  interesting  to  compare  this  statement,  quoted  word  for 
word  from  Kuss's  lectures,  with  what  CI.  Bernard  has  written  in 
a  recent  publication  :  — 

"  Recent  investigations,  which  are  still  unpublished,  lead  me  to 
heUeve  that  digestive  absorption  is  of  an  entirely  different  nature 
from  all  ordinary  absorption.  I  have  seen  the  pyloric  glands  of  a 
frog  disappear  during  winter,  when  digestion  ceased,  and  reappear 
in  the  spring,  when  digestion  recommences.  Experiments  which 
I  have  made  seem  to  show  that  on  the  surface  of  the  intestinal 
mucous  membrane  there  takes  place  an  actual  generation  of  epi- 
thelial elements  which  attract  the  alimentary  fluids,  elaborate 
them,  and  then,  by  means  of  a  kind  of  osmosis,  pour  them  into 
the  vessels.  Digestion  is  not,  therefore,  simply  a  direct  alimentary 
absorption.  The  aliments  dissolved  and  decomposed  by  the  diges- 
tive juices  in  the  intestine  simply  form  a  generating  blastema,  in 
which  the  digestive  epithelial  elements  find  the  materials  of  their 
composition  and  of  their  functional  activity,  hi  short,  I  do  not 
believe  in  what  may  be  called  direct  digestion.  There  is  an  organic 
or  vital  intermediate  process.  This  is  not  simply  a  chemical  solu- 
tion, as  most  physiologists  have  imagined.     I  hope,  in  time,  to  be 


260  DIGESTIVE  SYSTEM. 

noids  could  be  explained,  up  to  n  certain  point,  by  means  of 
the  physical  theories  of  osmosis,  but  the  passage  of  the 
fats  was  an  insoluble  problem,  of  which  the  only  explanation 
that  could  be  offered  was  that  emulsion  took  place,  or  even 
decomposition  or  disengagement  followed  by  reconstitution. 
We  have  seen  that  this  is  not  the  case,  and  that  the  fat  is 
naturally  absorbed.  This  view  is  confirmed  by  what  so  fre- 
quently takes  place  in  other  parts  of  the  organism :  the  plas- 
matic cells  of  the  deep  layers  of  the  dermis,  and  those  of  the 
mesentery,  are  quickly  filled  with  a  quantity  of  fat  which 
they  abstract  from  the  blood,  when  the  latter  gets  saturated 
with  it  by  means  of  abundant  nourishment;  this  fat  is  some- 
times very  quickly  given  up  again,  when  the  animal  grows 
suddenly  lean,  as  in  the  case  of  a  cholera  patient  whose 
orbital  fat  disappears  in  a  few  hours.  The  fatty  cells  may 
then  be  observed  to  lose  their  fat,  which  is  replaced  by  a 
serous  fluid,  which  disappears  in  its  turn,  while  the  globule 
returns  to  its  typical  condition  of  a  plasmatic  globule;  it 
cannot  be  urged  that  the  influence  of  any  special  dissolving 
fluid  is  here  exerted. 

This  fict  can  hardly  be  explained  except  by  supposing 
that,  in  order  to  penetrate  the  economy,  the  fatty  substances 
form,  with  the  albuminoid  substances,  special  combinations 
which  may  be  compared  with  what  we  find  in  the  medullary 
substance  of  the  nerves ;  this  instance  of  reabsorption  may 
also  be  made  use  of  in  endeavoring  to  discover  by  what  vas- 
cular organs  the  absorbed  fat  is  carried  off,  whether  by  the 
blood  vessels  or  the  chyliferous  vessels. 

We  have  now  to  see  what  becomes  of  the  epithelial  cells 
which  assist  the  passage,  and  what  becomes  of  the  substances 
wliich  pass. 

B.  Intestinal  desquamation.     Bile. 

After  having  conveyed  the  absorbed  fluids  (especially  the 
fat,  as  may  most  readily  be  ascertained)  to  the  tissue  of  the 

able  to  show  what  conclusions  we  must  draw  from  these  new  ideas 
on  the  subject."  (CI.  Bernard,  "  De  la  Physiologie  Generale." 
Notes,  1872,  p.  283.)  And  farther  on  (p.  287),  CI.  Bernard  adds: 
*'  If  the  cells  on  the  surface  of  the  intestine  be  withdrawn  horn 
the  work  of  digestion,  atrophy  speedily  ensues.  Thus  I  have 
found,  on  isolating  a  loop  of  the  intestine  in  such  a  manner  as 
to  prevent  the  passage  of  the  food,  that  atrophy  of  the  mucous 
membrane  soon  followed,  although  the  circulation  went  on  as 
usual." 


BILE.  261 

villus,  the  epithelium  of  the  villus  being  now  composed  only 
of  its  albuminous  elements,  more  or  less  liquefied,  begins  to 
fall  into  decay ;  fragments  of  it  were  long  since  found  to 
exist  in  the  intestine,  but  they  were  designated  under  the 
name  of  crude  chyle.  We  find  young  cellular  elements 
ready  to  take  the  place  of  this  decayed  epithelium. 

It  is  at  this  instant  only  (7  or  8  hours  after  the  ingestion 
of  the  food),  that  the  bile  is  poured  into  the  intestinal 
canal. 

The  hile  is  a  fluid  which  it  is  difficult  to  study  satisfactorily 
when  it  is  contained  in  the  biliary  or  gall-bladder  of  a 
corpse;  because,  under  these  conditions,  it  decomposes 
rnpidly,  especially  when  in  contact  with  the  mucus  of  this 
bladder;  its  color  and  its  reaction  are  then  changed.  In 
order  to  form  an  exact  idea  of  it,  a  fistula  should  be  opened 
at  the  bottom  of  the  gall  bladder,  through  the  coats  of  the 
abdomen,  care  being  taken  to  tie  the  cystic  duct  {ductus 
choledochus)^  lest  any  fluid  should  escape  into  the  intestinal 
canal.  In  this  way,  the  bile  may  be  collected,  and  the  flow  of 
the  secretion  will  be  found  very  abundant  and  almost  uninter- 
rupted, increasing  in  quantity,  however,  especially  at  a  certain 
period  of  digestion.  The  quantity  of  water  in  this  fluid  has 
been  estimated  in  the  ratio  of  20  to  1 :  the  solid  residuum  is, 
therefore,  5  grammes  to  100  grammes  of  bile.  On  the  other 
liand,  this  solid  residuum  represents,  for  24  hours,  a  mean 
AveiLiht  of  y^V^  part  of  the  weight  of  the  body  :  thus,  in  the 
case  of  man,  whose  mean  weight  is  65  kilogrammes,  we  find 
that,  in  24  hours,  the  anhydrous  bile  would  be  represented 
by  05  grammes ;  on  multiplying  this  figure  by  20,  we  obtain 
1  kilogramme,  300  grammes,  as  the  weight  of  the  bile  secreted 
in  24  hours. 

Under  these  circumstances  it  is  also  found  that  the  natural 
color  of  the  bile  is  not  green,  as  it  appears  in  autopsies  (being 
in;paired  by  the  mucus  of  the  vesicle),  and  as  it  is  some- 
times seen  in  vomited  matter  (being  then  changed  by  the 
action  of  the  gastric  juice).  The  natural  color  of  the  bile 
is  green  only  in  the  case  of  the  oviparous  animals  ;  in  all  the 
mammalia  it  is  yellow^  as  may  be  seen  in  persons  suflering 
from  reabsorption  of  the  bile,  the  yellowish  tinge  appearing 
in  all  the  tissues,  beginning  with  the  white  of  the  eye :  the 
white  of  the  eye  of  jaundiced  persons  is  always  yellow. 

We  ascertain,  finally,  that  the  normal  bile  is  quite  7ieutral; 
its  mixture  with  the  mucus  sometimes  imparts  to  it  an 


262  DIGESTIVE  SYSTEM. 

alkalinity  which  has  led  to  tlie  supposition  that  it  has  an 
important  share  in  the  process  of  digestion. 

It  may  be  said,  briefly,  to  be  composed  of  water,  containing 
in  solution  three  different  elements :  salts,  cholesterine,  and 
coloring  matter.^ 

1.  The  salts  of  the  bile  are  essentially  what  was  formerly 
designated  under  the  name  of  biline :  this  biline  is  now 
shown  (Demar^ais)  to  be  a  combination  of  soda  with  two 
fatty  acids,  cholic  acid  and  choleic  acid:  these  constitute  the 
cholatc  and  choleate  of  soda;  these  acids  are  also  designated 
under  the  names  of  Taurocholic  and  Glycocholic  (Tauro- 
cholate  and  Glycocholate  of  Soda)  both  being  formed  by  the 
same  acid,  united  in  the  one  case,  to  glycochol,  and,  in  the 
other,  to  taurine.  In  fishes  these  acids  are  combined,  not 
with  soda,  but  with  potash. 

It  is  generally  admitted  that  the  cholalic  acid  is  originated 
m  fatty  substances ;  indeed,  it  is  found  strongly  to  resemble 
the  oleic  acid,  for  instance;  it  is  not,  therefore,  a  nitrogenous 
substance.  Glycochol  we  know  to  be  a  nitrogenous  sub- 
stance, having  a  sweetish  taste,  and  being  derived  from 
collagenous  substances,  whence  the  name  of  sugar  of  gela- 
tine. Taurine  is,  also,  a  nitrogenous  or  azotic  principle,  but 
it  also  contains  sulphur,  and  its  decomposition  in  the  intes- 
tine assists  in  producing  sulphuretted  hydrogen. 

2.  Cholesterine  is  a  fatty  substance  which  is  not  saponifi- 
able ;  it  is  insoluble  in  water,  but  soluble  in  bile,  on  account 
of  the  choleate  of  soda  existing  in  the  latter;  if  the  quantity 
of  this  salt  is  insufficient,  the  cholesterine  is  precipitated, 
forming  those  calculi  so  frequently  found  in  the  biliary  reser- 
voir. Researches  by  Flint  seem  to  show  that  cholesterine  is 
a  waste  produced  by  the  life  ot  the  nervous  elements  (see  p. 
27). 

3.  The  coloring  matter  is  essentially  represented  by  bili- 
fulvine^  a  substance  strongly  resembling  the  blood  pigment 
'(ha3matoin)  from  which  it  is  derived;  it  is  decomposed 
and  precipitated  very  readily,  yielding  then  various  coloring 
matters,  designated  as  bilirubine,  biliverdine,  etc. :  green  is 
the  color  most  frequently  found  in  decomposed  bile. 

1  Table  showing  the  chemical  composition  of  the  bile  :  — 
Water 85  per  cent. 

r  Coloring  matter,  bilirubine    2  "j 

cr  ^' 3        .       Biliary  acids 8  I  -.p. 

So^^P^^'^^M  Cholesterine 4  f  ^^        " 

[Salts ij 


BILE,  263 

This  composition  and  the  properties  here  enumerated  sup- 
ply us  with  very  little  information  in  regard  to  the  probable 
functions  of  the  bile  in  digestion.  When  the  bile  is  turned 
out  of  its  course  by  a  fistula,  and  the  animal  is  prevented 
from  licking  the  wound,  so  that  the  bile  can  in  no  way 
enter  the  intestinal  canal,  the  animal  soon  becomes  ema- 
ciated :  absorj)tion  takes  place  incompletely,  especially  that 
of  the  fatty  substances  which  are  found  almost  entire  in  the 
excrement,  and  the  animal  can  only  be  kept  alive  by  receiv- 
ing twice  or  thrice  its  usual  quantity  of  food.  The  pilous 
system  of  the  animal  also  suffers  greatly :  the  hair  dries,  be- 
comes atrophied  and  falls;  we  shall  see,  however,  that  this 
is  due  to  the  fact  that,  in  its  natural  condition,  a  large  part 
of  the  bile  is  reabsorbed  in  the  intestinal  canal,  and  when  it 
flows  out  of  tlie  body  the  organism  suffers  a  great  loss,  espe- 
cially in  sulphur  (taui'ine)  since  there  are  at  least  3  grammes 
of  sulphur  in  the  bile  formed  during  24  hours ;  this  sulphur 
forms  an  important  part  of  all  the  elements  of  the  epidermis, 
esjiecially  the  horny  productions  (hair,  nails,  etc.). 

In  brief,  the  presence  of  the  bile  appears  to  be  necessary  to 
the  accomplishment  of  the  process  of  digestion  and  absorp- 
tion. But  how  does  it  act  ?  As  we  have  foreshadowed, 
and  upon  which  we  must  here  insist,  the  bile  is  not  poured 
into  the  intestine  in  such  a  manner  as  to  come  in  contact 
with  the  product  of  the  stomachal  digestion ;  when  the  bile 
enters  the  duodenum,  the  contents  of  the  intestine  have  al- 
ready extended  to  the  ileum,  or  even  to  the  large  intestine,  and 
have  been  absorbed  in  a  great  measure.  This  fact  alone,  as 
well  as  the  well-known  properties  of  the  normal  bile  (its 
neutrality,  especially),  renders  it  needless  to  attempt  to  dis- 
prove the  numerous  theories  which  have  been  suggested  as 
to  the  action  of  the  bile  on  the  chyme.^  Thus  it  was  said 
that  the  bile  being  alkaline,  and  the  chyme  acid,  these  two 
fluids  neutralized  each  other,  and  that,  from  the  product  of 
the  stomach,  the  bile  precipitated  a  crude  chyme  {chyme  brut), 
under  the  form  of  flakes;  these  we  have  already  shown  to  be 
simply  produced  from  the  epithelium  by  means  of  desquama- 
tion, which  may,  perhaps,  take  place  under  the  influence  of 
the  bile.  It  was  also  supposed  that  this  fluid  finely  divided 
or  made  an  emulsion  of  the  fats,  etc. 

Another  class  of  theories,  less  opposed  to  facts  than  the 

'  See  Blondlot,  "  Inutilite  de  la  Bile  dans  la  Digestion  proprc- 
mentdite."     Nancy,  1851. 


264  DIGESTIVE   SYSTEM. 

foregoing,  but  often  quite  as  hypotlietical,  makes  the  bile  to 
consist  of  a  fluid  which  opposes  the  putrid  fermentation  of 
the  contents  of  the  intestine;  indeed,  when  the  bile  is  turned 
out  of  its  course,  and  made  to  flow  outwards,  the  faeces  are 
found  to  acquire  a  very  fetid  odor.  The  bile  is  also  sometime 
supposed  to  be  an  excitant  of  the  mucous  and  of  the  intestinal 
muscle;  we  have  seen,  however,  that  the  erectile  action  of  the 
villi  belongs  entirely  to  the  epithelium,  and  takes  place  long 
before  the  arrival  of  the  bile,  under  the  exciting  influence  of 
the  gastric  juice  alone :  while,  on  the  other  hand,  changing 
the  natural  course  of  the  bile  out  of  the  intestine  produces 
no  efiect  on  the  motion  of  the  muscular  coats  of  this  canal. 

We  take,  finally,  for  our  starting-point,  the  fact  that  the 
bile  enters  the  intestine  only  when  the  process  of  absorption 
is  nearly  completed,  and  when  the  epithelium  which  has 
served  for  its  passage,  begins  to  decay  and  desquamate. 
The  bile  itself  then  appears  to  undergo  several  changes:  its 
coloring  matter  is  precipitated,  and  mixes  with  the  faeces, 
imparting  its  own  color  to  them ;  the  case  is  the  same  in 
regard  to  the  cholesterine,  which  is  an  excrementitial  prod- 
uct ;  the  remainder  of  the  bile  seems  to  disappear  in  the 
intestinal  walls,  and  to  become  reabsorbed,  not  in  its  simple 
form,  however,  for  none  of  its  acids  are  found  in  the  blood : 
it  appears  to  be  decomposed  in  the  very  act  of  penetrating 
the  intestinal  mucous  coat. 

This  assemblage  of  ficts,  including  the  well-known  one 
that  the  bile  speedily  dissolves  all  cellular  elements  (as  may 
be  easily  observed  in  the  blood  globules),  beside  the  circum- 
stance that  the  greatest  activity  of  the  epithelial  desquama- 
tion of  the  intestine  takes  ])lace  when  it  comes  in  contact 
with  the  bile;  all  justify  us  in  concluding  that  the  exudation 
and  the  action  of  the  bile  have  some  relation  to  this  decay 
of  the  epitheliums.  The  chief  purpose  served  by  the  bile  is 
thus  the  renewal  of  the  cellular  coats,  promoting  the  decay 
of  the  old  elements,  and  the  restoration  of  the  new :  if  we 
may  be  allowed  the  expression,  it  sweeps  the  workshop  clean^ 
ill  which  the  laborious  task  of  absorption  has  just  been  com- 
pleted^ and  forms  new  epithelial  organs  ready  to  begin  the 
process  over  again.  This  reconstitution  takes  place  by 
means  of  the  fresh  cells  which  exist  in  the  deeper  portion 
of  the  epithelium.  The  intestine  is,  thus,  never  unprovided 
with  epithelial  cells:  the  new  generation  takes  place  so 
rapidly  that  it  is  impossible  to  distinguish  it,  half-hidden  as 
it  is  by  the  ruins  of  former  cells.     We  have  seen  that  when 


FUNCTIONS  OF  TEE  LIVER.  265 

the  bile  is  allowed  to  pass  out  of  the  body  without  going 
through  the  intestinal  canal  animals  lose  their  power  of 
absorption,  especially  of  fatty  substances  :  they  continue  in 
health,  but  require  two  or  three  times  their  usual  quantity 
of  food.  Digestion,  properly  so-called,  is  not,  therefore, 
impaired ;  it  is  oniy  absorption,  especially  of  fats,  which  is 
insufficient  (since  absorption  is  the  process  which  requires  the 
greatest  activity  on  the  part  of  the  epithelium) ;  the  bile 
appears  to  be  connected  with  the  absorption  of  the  fatty 
substances,  by  increasing  the  activity  of  the  processes  of 
renovation,  desquamation,  and  vegetation  of  the  epithelium. 

C.  Functions  of  the  Liver. 

The  share-  taken  by  the  bile  in  intestinal  functions,  espe- 
cially in  absoi-ption,  has  already  shown  us  the  physiological 
importance  of  that  large  viscus  called  the  liver ;  we  have 
seen  that  this  organ  has  some  effect  upon  the  composition 
of  the  blood,  the  formation  and  destruction  of  its  globular 
elements,  particularly  the  red  globules  (see  bloody  p.  124). 
CI.  Bernard's  researches  have  finally  revealed  new  functions 
in  this  organ,  glycogeny^  showing  it  to  have  at  least  as  much 
effect  on  the  constitution  of  the  serum  as  on  that  of  the 
morphological  or  physical  elements  of  the  blood. 

We  have  already  said  (p.  233)  that  the  liver  is  formed  of 
two  glands,  each  of  which  penetrates  the  other;  namely  the 
biliary  gland  and  the  vascular  blood  gland  (Fig.  70).  We 
liave  studied  the  functions  of  the  biliary  gland ;  which  are 
quite  independent  of  those  of  the  vascular  gland,  especially 
from  the  stand-point  of  glycogeny  (CI.  Bernard) ;  study  of 
the  development  of  the  liver  from  the  embryo  serves  to  ex- 
hibit this  independence,  especially  in  an  anatomical  point  of 
view  (C.  Morel.  See  p.  232.)  Numerous  and,  perhaps,  still 
more  interesting  proofs  of  it  are  to  be  found  in  the  facts 
borrowed  from  [)athology. 

Thus,  in  cirrhosis  of  the  liver,  an  affection  of  the  connective 
tissue  of  this  organ,  although  the  great  hepatic  cells  (glyco- 
genic liver),  are  impaired  by  compression,  or  even  destroyed, 
the  secretion  of  the  bile,  and,  later,  its  pathological  reabsorjv 
lion  (jaundice)  goes  on  as  Uvsual,  the  canaliculi,  or  secreting 
tabes,  of  the  bile  not  having  been  first  attacked. 

'^iiha  fatty  degeneration  of  the  liver,  which  affects  only  the 
larger  cells,  produces  no  change  in  the  secretion  of  the  bile ; 
and  in  very  large  livers  whose  substance  has  been  changed 
almost  entirely  into  fat,  a  considerable  quantity  of  bile  is  still 


266 


DIGESTIVE  SYSTEM, 


found  in  the  gall-bladder  and  in  the  tubes,  the  biliary  liver 
remaining  comparatively  uninjured.  If  the  larger  cells  were 
the  secreting  element  of  the  bile,  it  would  be  impossible  to 


f^'~|'Ho| 


^•2  s.H  «  g 
^  tl;  -  g-  -  ?-. 


comprehend  how  secretion  could  continue ;  these  cells  when 
thus  completely  infiltrated  with  fat,  from  a  physiological  point 
of  view,  are  only  defunct  globules.^  Numerous  and  recent 
histological  researches,  however,  having  for  their  object  the 


^  See  P.  A.  Accolas,  "  Essai  aur  I'Origine  des  Canalicules  Ilepa- 
tiques,  et  sur  I'lndependance  des  Appareils  Biliaire  et  Glycogene 
du  Foie."     Thiise  de  Strasbourg,  1867,  No.  19. 


FUNCTIONS  OF  THE  LIVER.  267 

origin  of  the  hepatic  canaliculi,  seem  to  show  a  connection 
between  the  Large  hepatic  cells  and  the  bihnry  organs,  which 
is,  perhaps,  closer  than  that  indicated  by  Kiiss,  Morel,  Hand- 
field  Jones,  and  Ch.  Robin  (Diet,  de  Nysten).  The  agree- 
ment of  the  results  obtained  by  numerous  histologists,  in 
France  (Robin,  Legros,  Cornil),  as  well  as  in  other  countries 
(Gerlach,  Andrejevie,  MacGillavry,  Chronszewsky,  Hering, 
Eberth,  etc.),  obliges  us  to  consider  these  researches  of  im- 
portance, and  we  shall  find  that  physiological  data  correspond 
with  these  results.^ 

Lereboullet  was,^  1853,  convinced  by  his  experiments  on 
the  fatty  liver,  that  the  origins  of  the  biliary  tubes  are  simply 
empty  spaces  which  are  arranged  in  series  (intercellular 
meati),  hollowed  out  between  the  cells:  these  empty  spaces 
are  entirely  accidental,  and  would  be  produced  in  anatomical 
preparations  by  the  passage  of  the  injected  matters. 

These  spaces  have  been  the  subject  of  much  investigation : 
they  are  known  by  the  name  of  biliary  capillaries^  or  intra- 
lobular canaliculi.  Kolliker,  as  well  as  the  other  histologists 
whom  we  have  mentioned,  has  succeeded  in  distinguishing 
them,  and  considers  them  to  be  simply  intercellular  lacuuce 
having  no  pro])er  coats,  or  being  covered  only  with  a  sort  of 
cuticle  which  Kolliker  looks  upon  as  belonging  to  the  cells 
between  which  the  lacuna  is  situated :  "  I  should  prefer  to 
consider  this  cuticle  as  a  cellular  membrane,  and  to  say  that 
it  is  more  developed  in  the  region  of  the  biliary  capillaries 
than  in  any  other  part."  (French  trans.  1870,  p.  5G8.) 
.  According  to  some  anatomists  (MacGillavry,  Frey),  these 
canaliculi  are  furnished  with  a  coat  of  their  own,  the  large 
hepatic  cells  being  situated  outside ;  Legros'  researches  show 
that  this  coat  is  lined  with  a  pavement  epithelium.  We  are 
finally  brought  back  to  the  idea  of  a  biliary  gland,  which  is 
quite  distinct  from  the  vascular  blood  gland,  although  the 
mutual  association  between  these  two  organs  appears  much 
closer  than  the  researches  made  five  or  six  years  ago  would 
lead  us  to  suppose.  "In  the  interlobular  ducts  the  epithe- 
lium is  more  distinctly  columnar  than  in  the  branches  of  the 
hepatic  duct  properly  so  called :  but  in  the  intralobular 
canaliculi^  it  is  a  true  pavement  of  small  cells,  which,  by 
their  proximity  to  the  secretory  canaliculi,  form  the  coats 

'  Lereboullet,  "  IMemoire  sur  la  Structure  intime  du  Foie  et  sur 
la  Nature  de  1' Alteration  coiiuue  sous  le  Nom  de  Foie  Gras." 
Paris,  1853,  in  Ito. 


268  DIGESTIVE  SYSTEM. 

of  these  vessels ;  these  cells  thus  form  an  organ  quite  distinct 
from  the  much  larger  one  constituted  by  the  hepatic  cells, 
property  so  called  (Ch.  Robin,  "Du  Microscope,"  1871). 

The  final  results  obtained  by  histology  are  not  thus  op- 
posed to  the  physiological  distinction  made  between  a  biliary 
and  a  glycogenic  gland.  It  appears,  however,  that  the  great 
question  of  the  physiology  of  the  liver  is  not  yet  solved ;  for 
recent  physiological  and  experimental  researches  seem  to 
show  that  the  glycogenic  function  is  by  no  means  peculiar 
to  this  organ,  as  was  at  first  so  firmly  believed,  but  is  a 
property  common  to  all  the  tissues,  and  only  carried  to  a 
slightly  higher  degree  in  the  hepatic  organ.  These  re- 
searches are  chiefly  connected  with  the  study  of  diabetes, 
and,  with  regard  to  this  disease,  we  shall  see  that  it  is 
going  too  far  to  completely  deny  the  glycogenic  functions 
of  the  liver  (Yulpian,  Cours  de  mai,  1872). 

CI.  Bernard  first  proved  that  animal  as  well  as  vegetable 
organisms  produce  sugar.  Magendie  had,  before  this,  dis- 
covered sugar  in  the  blood,  but  in  the  herbivorous  animals 
only ;  CI.  Bernard  proved  that  it  also  exists  in  the  carnivora, 
but  that  scarcely  any  signs  of  it  are  found  in  the  portal  vein, 
while  a  comparatively  large  quantity  is  found  in  the  hepatic 
veins.  He  also  showed  that  the  presence  of  this  sugar 
cannot  be  accounted  for  by  any  such  storing  up  of  the 
saccharine  elements  of  the  food  received  as  occurs  in  the 
case  of  certain  poisons,  but  that  sugar  exists  in  the  liver 
quite  independently  of  external  supply.  The  sugar  produced 
in  the  liver  he  show^s  is  similar  to  that  found  in  the  urine  of 
patients  suffering  from  diabetes,  and  that  this  disease  is  only 
a  pathological  exaggeration  of  the  normal  glycogenic  func- 
tion. This  function  of  the  liver  begins  in  the  foetus,  appar- 
ently only  at  the  age  of  three  or  four  months:  before  this 
time,  the  placenta  seems  to  perform  a  similar  ofiice,  by  means 
of  a  layer  of  glycogenic  cells,  placed  between  the  foetal  and 
maternal  placenta  (CI.  Bernard,  1847-1855). 

CI.  Bernard  soon  became  convinced  that  the  globular  ele- 
ments of  the  liver  do  not  form  sugar  directly,  but  rather  that 
there  is  a  substance  which  is  capable  of  being  transformed 
into  sugar,  a  glycogenosis  substasice  resembling  starch,  and 
which  is  changed  into  glucose  by  means  of  the  same  agents 
as  starch.  This  glycogenous  substance  can  only  be  changed 
into  sugar  in  the  organism  by  the  action  of  a  ferment  which 
is  produced  in  the  liver,  or  brought  into  it  by  the  blood. 
Bernard  became  convinced  of  this  by  observing  that  the 


FUNCTIONS  OF  THE  LIVER.  269 

quantity  of  sugar  in  the  liver  varies  according  to  the  circum- 
stances under  which  it  is  examined ;  if,  immediately  after  the 
death  of  the  animal,  it  is  always  found  to  contain  less  sugar 
than  on  the  following  day ;  this  is  because  the  glycogenous 
matter  is  changed  into  sugar  after  death  (CI.  Bernard,  1855, 
1859).  Schiff,  on  meeting  with  this  glycogenous  matter, 
gave  it  the  name  of  inuline,  wrongly  supposing  it  to  resem- 
ble a  vegetable  starch,  although  it  has  neither  the  same 
microscopical  features  nor  the  same  reactions.  Rouget  gave 
this  substance  the  name  of  zoa7nyU7ie  (or  animal  starch). 

CI.  Bernard  then  attached  great  importance  to  the  glyco- 
genic function  of  the  liver,  and  he  considered  sugar  as  an 
essential  element  in  the  composition  of  those  fluids  in  which 
cells  are  developed :  he  believed  that  he  saw  cases  of  spon- 
taneous generation  in  saccharine  fluids;  he  looked  upon 
sugar  as  the  most  indispensable  principle  of  the  life  of  the 
organic  elements ;  he  even  went  so  far  as  to  attribute  the 
almost  certain  death  of  those  animals,  whose  two  pneumo- 
gastric  nerves  have  been  cut,  to  the  fact  that  by  this  means 
the  glycogenic  functions  of  the  liver  are  arrested. 

These  exaggerations  produced  a  strong  reaction,  and  the 
attacks  made  upon  the  theory  of  glycogeny  brought  about 
the  discovery  of  some  important  facts.  The  theory  was 
defended  by  CI.  Bernard,  Lehmann,  and  Poggiale,  and  dis- 
puted principally  by  Figuier,  Colin,  Chauveau,  and  Sanson. 
Sanson  proved  that  meat,  muscular  flesh,  contains  a  saccha- 
rine substance,  and  that  an  extraordinary  quantity  of  this 
substance  is  produced  in  the  animals  experimented  upon,  by 
feeding  them  with  butcher's  meat ;  this  muscular  sugar  is, 
however,  dextrine  and  has  no  connection  with  the  glyco- 
genous substance  of  the  liver.  Rouget  showed  that  this 
glycogenous  matter,  or  zoamyline,  is  not  at  all  peculiar  to  the 
hepatic  tissue ;  that  it  represents  a  collateral  product  of  the 
nutrition  of  all  the  tissues,  and  is  chiefly  found  in  large  quanti- 
ties in  the  fcfitus  and  in  young  subjects:  first, in  the  bone-car- 
tilages of  the  members;  then  in  the  muscles  (the  muscular 
plasma  only)  ;  then  in  all  the  epitheliums,  from  the  epithelium 
of  the  placenta,  between  the  foetal  and  the  maternal  organism, 
to  the  epidermis,  the  pulmonary  vesicles,  and  the  glands  of 
Lieberkuhn,  and,  finally,  to  the  epithelium  of  the  vagina, 
wiiere  it  is  found  even  in  the  adult  female.  He  considers 
glycogeny  as  a  general  feature  of  the  life  of  the  tissues,  and 
its  exaggeration  as  an  accidental  circumstance  in  the  nutrition 
of  the  liver. 


270  DIGESTIVE  SYSTEM. 

With  regard  to  diabetes,  the  disease  which  first  gave  rise 
to  the  whole  question,  and  to  which  it  must  always  be  re- 
ferred in  physiological  investigations,  as  well  as  in  pathogenic 
researches,  it  must  be  admitted  that  the  liver  is  the  chief 
actor,  without,  however,  attributing  to  hepatic  glycogeny  the 
important  physiological  function  at  first  ascribed  to  it  by  CI. 
Bernard. 

Does  the  glycogenous  substance,  however,  which  in  path- 
ological cases  is  undoubtedly  changed  into  sugar,  constantly 
undergo  in  a  more  or  less  decided  degree  the  same  trans- 
formation when  in  the  physiological  state?  When  the 
animal  is  living  and  in  perfect  health,  does  the  liver  elabo- 
rate sugar  incessantly  ?  Here  this  vexed  question  of  glyco- 
geny rests  for  the  present.  CI.  Bernard  has  no  hesitation  in 
supposing  this  incessant  physiological  transformation.  In 
this  opinion  he  is  opposed  by  Schiff  and  Pavy.  These  two 
experimenters  maintain  that  the  sugar  found  in  the  liver  is 
always  formed  after  death :  in  a  fresh  liver,  taken  from  an 
animal  just  killed  (Pavy,  Schiff,  Ritter),^  or,  better  still,  from 
a  living  animal  (Meisner,  Jager),  no  sugar  will  be  found,  but 
only  glycogenous  matter  which  is  not  transformed  into 
sugar  in  the  living  animal,  either  for  want  of  a  ferment 
which  is  capable  of  producing  this  transformation  (Schifi*), 
or  because  this  ferment,  though  existing,  cannot  act  during 
the  life  of  the  animal  on  account  of  certain  influences  arising 
in  the  nervous  system  which  are  opposed  to  it  (Pavy). 

This  view  is,  evidently,  an  exaggerated  one.  These  ex- 
periments merely  show  that  in  the  normal  condition  the 
transformation  into  sugar  is  very  trifling,  and  not  easily 
exhibited  by  means  of  the  reagents  which  we  possess.  An 
American  physiologist,  however,  Dalton,  experimenting  with 
a  care  and  rapidity  at  least  equal  to  that  displayed  by 
Pavy,  has  succeeded  in  demonstrating  that  the  living  liver  is 
not  entirely  without  sugar. 

The  liver  thus  forms  glycogenous  matter :  this  matter  is 
changed  into  sugar  by  the  action  of  a  ferment  the  origin  of 
which  is  as  yet  undecided.*^ 

1  See  Schiff,  "  Nouvelles  Recherches  sur  la  Glycogenie  Ani- 
male."  (In  Journ.  de  I'Anat.  et  de  la  Physiol.,  de  Ch.  Robin, 
1866,  Nos.  de  juillet  et  aout.) 

2  Claude  Bernard's  researches  on  the  subject  of  glycogeny  may 
be  summed  up  in  the  following  manner:  "  In  1848  he  discovered 
sugar  in  the  liver;  it  is  always  found  there,  whatever  may  be  the 
nutrition  of  the  animal.     In  1855  he  demonstrates  that  the  sugar 


FUNCTIONS   OF  THE  LIVER.  271 

The  sugar  thus  formed  is  poured  into  the  blood,  and,  being 
drawn  on  by  the  current  of  the  circulation,  soon  disappears, 
being  either  consumed  in  the  lungs  or  destroyed  by  oxida- 
tion, or  by  some  other  means  in  some  part  of  the  economy. 
In  this  way  little  or  no  sugar  is  left  in  the  blood,  but  when- 
ever the  quantity  formed  is  too  considerable,  and  is  not  com- 
j^letely  destroyed,  glycaemia  ensues;  and  if  the  quantity 
exceed  three  per  cent  of  the  solid  residuum  of  the  blood,  or 
if  it  is  more  than  from  two  to  three  grammes  to  every  kilo- 
gramme of  the  animal's  weight  (Kuhne),  the  sugar  is  excreted 
by  the  kidneys,  and  the  glycaamia  appears  as  glycosuria  or 
diabetes. 

This  increase  in  the  production  of  sugar,  and  the  conse- 
quences which  follow,  may  be  artificially  produced  by  various 
methods,  which  confirm  the  theory  of  hepatic  glycogeny,  by 
more  or  less  directly  aflfecting  the  liver. 

Thus  the  injection  of  irritants  into  the  portal  vein  (ether, 
Harley)  brings  on  glycosuria.  This  is,  no  doubt,  the  efi*ect 
of  certain  more  or  less  poisonous  substances  when  absorbed 
by  different  organs,  such  as  chloroform,  woorara  (?),  putrid 
matters,  etc. :  the  latter,  no  doubt,  help  to  increase  the  fer- 
ment necessary  to  change  the  glycogen  into  sugar.  All  those 
conditions,  in  fact,  which  are  favorable  for  fermentations 
serve  to  produce  and  increase  diabetes,  while  all  those  which 
hinder  fermentation  tend  to  diminish  or  even  to  check  it 


of  the  liver  is  derived  from  a  substance  formed  in  the  liver,  which 
substance  he  examines  (1857),  finding  in  it  features  resembling 
those  of  vegetable  starch.  In  1859,  while  seeking  for  the  origin 
of  this  glycogenous  substance^  he  found  it  to  exist  in  the  placental 
organs  of  the  mammalia,  in  the  vitelline  membrane  of  birds,  and 
in  the  inferior  animals  when  in  the  larval  or  chrysalid  state.  He 
then  shows  that  the  glycogenic  cells  are  first  found  on  the  inner 
surface  of  the  amnion  of  the  mammalia,  where,  about  the  middle 
of  gestation,  they  form  well  developed  papillae,  disappearing  after- 
wards when  the  glycogenic  function  becomes  established  in  the  liver. 
In  birds  the  glycogenic  cells  are  first  placed  along  the  passage  of 
the  omphalo-raesenteric  veins,  and  then  at  the  extremities  of  the 
vitelline  veins,  which  form  actual  glycogenic  villi  floating  in  the 
substance  of  the  yolk.  The  glycogenic  substance  is  thus  at  first 
diffused  throughout  the  organs  of  the  embryo  in  a  transitory  form, 
and  only  finally  appears  in  the  liver,  where  it  remains.  On  the 
other  hand,  animal  glycogeny  really  constitutes  a  chemical  evolu- 
tion of  the  starchy  elements,  an  evolution  v/hich  resembles,  or, 
rather,  is  identical  with  that  exhibited  by  the  starch  found  in  vege- 
table organisms  (CI.  Bernard,  Cours  de  1872). 


272 


DIGESTIVE  SYSTEM. 


entirely.  Thus  Wingradoff  has  shown  that  frogs,  in  which 
this  disease  has  been  produced,  recover  if  put  in  a  cold 
place,  a  low  temperature  serving  to  check  femientation  ;  but 
the  disease  reappears  if  the  animal  be  replaced  in  an  atmos- 
phere sufficiently  warm  to  allow  of  fermentation  taking  place.^ 
The  most  remarkable  case,  however,  of  diabetes  artificially 
produced  is  that  in  which  it  is  caused  by  special  modifications 
wrought  in  the  nervous  system.  CI.  Bernard  discovered  that 
if  a  puncture  be  made  in  the  floor  (in  P',  Fig.  71)  of  the  fourth 
ventricle  of  an  animal  (a  rabbit),  between  the  roots  of  the 

auditory  and  those  of  the 
pneumogastric  nerves,  sugar 
is  found  a  short  time  after- 
wards (an  hour  and  some- 
times less)  in  the  urine  of  the 
animal.  (A  puncture  made 
a  little  higher  up,  as  at  P, 
produces  glycosuria,  accom- 
panied by  polyuria ;  a  little 
higher  up,  the  puncture  pro- 
duces albuminuria.)  This 
glycosuria  is  caused  by  the 
hepatic  function,  Wingra- 
doff having  shown  that  if 
the  fourth  ventricle  of  a 
frog  be  pricked,  thus  pro- 
ducing diabetes,  the  disease  will  disappear  if  the  liver,  which 
is  the  sugar-producing  organ,  be  removed.  We  know,  on 
the  other  hand,  that  after  a  long  course  of  slow  poisoning  by 
arsenic  the  liver  loses  its  glycogenous  matter  and  thus  the 
power  of  producing  sugar;  and,  in  this  case,  a  puncture  in 
the  fourth  ventricle  of  an  animal  does  not  produce  diabetes. 
The  nerve-tract  which  unites  the  fourth  ventricle  to  the 
liver  appears  to  belong,  not  to  the  pneumogastric,  but  to  the 
great  sympathetic  nerve,  as  was  imagined  by  CI.  Bernard, 
and  directly  proved  by  Schiff  and  Moos :  the  latter,  espe- 


Fig.  71.  —  Fourth  ventricle  (rabbit)  and 
experimental  punctures.* 


1  See  CI.  Bernard,  '*  Cours  du  College  de  France."  (In  Revue 
des  Cours  Scientifiques,  avril,  1873.) 

*  The  lobes  of  the  cerebellum  are  separated :  below  are  seen  the  restif orm 
bodies  whose  divergence  surrounds  the  point  of  the  calamus  scriptorius  and  the 
fourth  ventricle.  The  puncture  P',  whicli  produces  (^lycoswiia,  is  situated  a  little 
above  the  point  of  the  calamus.  The  puncture  P  is  made  at  the  level  of  the 
tubercles  of  Wenzel ;  that  is  to  say,  the  origin  of  the  auditory  nerves.  (CI.  Ber- 
nard.) 


ORGANS  OF  ABSORPTION.  273 

cially,  has  shown  that,  if  all  the  sympathetic  nerves  leading 
to  the  liver  of  a  frog  be  tied,  diabetes  can  no  longer  be  pro- 
duced, either  by  puncture  of  the  fourth  ventricle  or  by  elec- 
trical excitation  of  the  spinal  cori.  In  all  these  cases  violent 
hyperaeniia  of  tlie  liver  appears  to  be  necessary  to  the  excite- 
ment of  its  glycogenic  functions;  indeed,  if  the  inferior 
vena  cava  below  the  liver  in  a  frog  be  tied,  an  increase 
of  circulation  in  the  portal  vein  is  produced,  followed  by 
diabetes.  This  increase  of  circulation  is  caused  by  the 
anastomoses  existing  in  this  animal,  between  the  venous  sys- 
tem in  general  and  the  system  of  the  portal  vein.  The  con- 
gestion of  the  liver  and  excitation  of  its  glycogenic  function 
which  follow  a  puncture  made  in  the  fourth  ventricle  do  not, 
however,  appear  to  be  produced  simply  by  a  (nervous)  para- 
lytic hypera3raia,  arising  from  the  abolition  of  the  vaso- 
motor innervation;  because  the  artificial  diabetes  thus 
produced  is  but  temporary  (lasting,  at  the  most,  twenty-four 
hours).  This  diabetes  appears  rather  to  arise  from  the  excita- 
tion of  certain  nerves  included  in  the  network  of  the  great 
svmpathetic  nerve,  and  which  are  to  the  liver  what  the 
chorda  tympani  is  to  the  sub-maxillary  gland  (CI.  Bernard). 

D.  Organs  of  absorption.  —  Inunction  of  the  chyliferouB 

vessels. 

We  have  seen  how  the  digested  matters  reach  the  very 
substance  of  the  villus  by  means  of  the  epithelium.  While 
the  epithelium  is  being  renewed  (desquamation,  etc.),  the 
body  of  the  villus  empties  its  contents,  and  the  absorbed 
elements  are  difiiised  into  or  through  the  vessels. 

These  vessels,  however,  are  of  two  kinds :  we  have  seen 
that  there  is  a  vascular  blood  network,  forming  the  origin  of 
the  portal  vein,  and  a  central  chyliferous  vessel,  the  origin 
of  the  chyliferous  vessels,  which  open  into  the  principal  trunk 
of  the  lymphatic  circulation  (thoracic  duct.  See  lymphatic 
sj/stem,  p.  156).  The  blood  current,  being  placed  so  near 
the  surface,  is  evidently  in  the  most  favorable  situation  to 
absorb  whatever  is  brought  to  it  by  the  epithelium:  it  is, 
therefore,  generally  supposed  that  the  greater  part  of  the 
absorbed  matters  are  carried  along  by  the  blood ;  and  it  is 
true  that  we  find  the  peptones  and  glucose  again  in  the 
portal  vein.  But,  while  the  fat  is  disappearing  from  the  villus, 
we  find  that  the  central  chyliferous  vessel  becomes  quite  white, 
and  that  a  large  number  of  delicately  emulsionized  fat  mole- 
cules make  their  appearance  in  it ;  this  seems  to  show  that 

18 


274  DIGESTIVE  SYSTEM. 

the  fats  do  not  pass  through  the  same  organs  as  the  preced- 
ing substances,  and  that  the  chyliferous  vessel  is  especially 
appointed  for  their  absorption. 

We  may,  indeed,  suppose  that  the  fat  contained  in  the 
intestine,  is  absorbed  by  the  cells  of  the  villus  (epithelial  and 
plasmatic  cells),  and  that  it  is  excreted  by  them  into  the 
central  chyliferous  vessel.  We  have  already  considered  the 
lymphatic  vessels  as  appointed  to  collect  the  deeper  resi- 
duum, the  waste  produced  by  the  life  of  the  epitheliums 
(see  p.  194). 

The  fa]t  does  not,  however,  pass  through  the  lymphatic 
organs  only;  it  is  also  found  in  the  blood,  although  the 
quantity  there  is  very  small.  The  other  matters  which  have 
been  absorbed  are  also  met  with  in  the  chyliferous  vessels, 
but  their  quantity,  compared  with  that  of  the  fat,  is  infini- 
tesimal ly  small. 

Some  authors,  however,  entirely  deny  that  the  vessels  of 
the  portal  circulation  have  the  power  of  absorbing  and 
carrying  off  the  fat.^  This  is  because  the  fat  found  in  the 
blood  is  not  in  the  same  state  as  in  the  chyle :  in  mammal's 
blood  the  fat  is  never  in  a  free  state,  but  always  saponified  ; 
it  is,  no  doubt,  saponified  by  the  choleate  of  soda  in  the  bile. 

Most  poisonous  substances  are  absorbed  by  the  veins; 
intoxication  taking  place  so  rapidly  that  the  poisons  can 
scarcely  be  supposed  to  pass  through  the  lymphatic  organs. 

Metals  absorbed  in  the  form  of  metallic  salts,  accumulate 
in  the  liver.  This  is  an  impoi-tant  fact,  for  it  shows  that  the 
liver  retains  a  large  proportion  of  the  alimentary  substances 
for  the  purpose  of  modilying  them.  The  albumen  is  trans- 
formed, because  it  comes  in  contact  with  the  hepatic  cells  by 
means  of  the  portal  circulation. 

We  find,  in  short,  that  our  knowledge  of  this  interior 
process  of  absorption  is  still  very  incomplete.  We  have 
been  occupied  in  studying  these  phenomena  in  reference  to 
the  living  cells  in  which  absorption  takes  place,  and  we  have 
considered  the  process  of  absorption  as  an  essential  feature 
of  these  globules.  We  have,  therefore,  paid  little  attention 
to  the  physical  theories  of  absorption,  or  to  experiments  made 
with  membranes  deprived  of  life.  Experiments  of  this  kind 
have  led  to  the  belief  that  absorption  is  simply  a  phenomenon 
of  osmosis.     Thus  J.  Beclard  considers  the  current  of  absorp- 

*  See  Beclard,  "  Recherches  Experimentales  sur  les  Fonctions 
de  la  Veine  Porte."   (Arch.  Gene'r.  de  Medecine,  1818.) 


LARGE  INTESTINE.  275 

tion  as  produced  by  the  difference  in  the  specific  heat  of 
those  fluids  which  surround  the  membrane  to  be  traversed  : 
he  looks  upon  the  osmosis  which  then  takes  place  as  a 
physico-chemical  property,  in  virtue  of  which  the  miscible 
fluids  have  a  tendency  to  mix  in  the  membrane,  one  current 
predominating  over  another.  All  other  things  being  equal, 
the  direction  and  intensity  of  the  current  are  determined  by 
the  differences  in  specific  heat.  The  figures  given  by  J. 
Beclard,  in  support  of  this  theory,  showing  the  specific  heat 
of  the  different  fluids,  agree  perfectly  with  what  we  know  of 
their  flowing  towards  each  other.  However  plausible  this 
theory  may  appear,  it  is  only  a  physical  theory  of  osmosis / 
and  knowing,  as  we  do,  the  important  function  of  the  living 
cell,  we  cannot  imagine  that,  in  the  phenomenon  of  intestinal 
absorption,  it  simply  plays  the  part  of  an  inert  membrane. 

V.   Large  Intestine. 

The  aliments  that  pass  out  from  the  stomach  form  a 
fluid  mass ;  we  have  seen  that  they  become  still  more  fluid 
by  the  addition  of  the  pancreatic  and  enteric  juices.  How- 
ever, as  these  matters  pass  through  the  small  intestine,  their 
consistency  increases,  while  their  bulk  diminishes,  the  greater 
part  being  absorbed.  The  small  intestine,  therefore,  delivers 
to  the  large  intestine  only  a  solid  substance,  or  waste,  which 
is  to  be  thrown  off,  and  is  prevented  Irom  passing  back  again 
by  the  ileo-ccBcal  value,  which  i-enders  any  reflux  impossible. 
In  man,  very  little  digestive  action  takes  place  in  the  large 
intestine;*  the  small  amount  which  has  escaped  absorption 
are  here,  however,  drawn  into  the  blood  current,  and  the 
large  intestine  may  even  absorb  fluids  directly  introduced 
into  it.  After  injection,  by  the  rectum,  of  fatty  substances 
(fats  in  a  state  of  emulsion),  the  lympliatic  vessels  leading 
from  the  large  intestine  exhibit  the  same  features,  the  same 
chyliferous  appearance,  as  those  of  the  small  intestine.  The 
villi  are  not  found  here,  but  their  place  is  supplied  by  nu- 
merous folds  in  the  mucous  membrane.  In  herbivorous  ani- 
mals, whose  caecum  is  very  much  developed,  this  part  of  the 
intestinal  tube  is  the  seat  of  actual  digestive  phenomena : 
the  coecum  may  therefore  be  considered  as  a  sort  of  second 
stomach  ;  it  contains  acids  which  sufiace  for  the  digestion  of 
the  vegetable  albuminoids.  It  is  not  certain  that  these 
acids  are  secreted  from  its  walls :  they  are,  more  probably, 
produced  by   the   aliments  themselves.      They  increase  in 


276  DIGESTIVE  SYSTEM. 

quantity  with  the  increase  of  substance  in  the  canal.  These 
acids  are  generally  the  lactic  and  butyric  acids,  arising  from 
the  fermentation  and  decomposition  of  the  sugars  and  the 
fats. 

Half-way  through  the  large  intestine,  however,  all  digestion 
and  absorption  cease :  the  tube  contains  only  those  matters 
which  are  to  be  thrown  off,  —  the  fceces,  in  short.  The  fajces 
have  been  wrongly  considered  as  principally  formed  of 
that  part  of  the  food  which  cannot  be  assimilated :  if  this 
were  true,  if  all  the  nourishment  received  can  be  absorbed, 
there  ought  to  be  no  faeces,  and  yet  they  appear,  even  in  this 
case.  Thus  the  foetus,  whose  digestive  tube  is  as  yet  empty, 
immediately  after  birth  expels  faeces  which  are  well  known 
under  the  name  of  meconium:  the  meconium  is  formed  of 
remains  of  epithelial  cells,  colored  yellow  by  the  bile,  which, 
not  having  yet  become  decomposed,  preserves  its  natural 
color.  This  explains  why  the  principal  product  thrown  off,  and 
of  which  the  faeces  are  chiefly  composed,  consists  of  remains 
of  the  desquamated  epithellmn:  sometimes,  even  in  the 
adult,  these  remains  alone  form  the  substance  of  the  faeces. 
They  appear  either  as  entire  or  as  mutilated  globules  of  a 
whitish  color,  variously  tinged  by  the  decomposed  bile. 
These  epithelial  remains  somewhat  resemble  the  fine  scales 
which  fall  from  the  cutaneous  epidermis,  but  they  are  more 
numerous  and  important  than  this;  for  we  have  seen  that 
the  shedding  of  the  epithelium  is  the  fxtal  termination  of  the 
series  of  phenomena  of  absorption,  and  that  the  principal 
use  of  the  bile  is  to  regulate  and  to  hasten  its  production. 

Those  parts  of  the  aliments  and  of  the  digestive  fluids 
which  cannot  be  assimilated  can  only  be  classed  as  secondary 
elements  in  the  constitution  of  the  faeces.  Among  these  are 
cholesterine  and  the  coloring  matter  of  the  bile  which  are 
precipitated  when  this  fluid  enters  the  intestine ;  also  fatty 
substances,  when  ingested  in  too  large  quantities ;  amylaceous 
substances  protected  by  too  thick  a  covering  of  cellulose ; 
and  cellulose,  in  general,  with  its  derivatives.  Indeed  vege- 
table aliments  contain  the  largest  quantity  of  substances 
which  resist  digestion,  and  the  faeces  of  the  herbivorous  ani- 
mals arCy  therefore,  much  more  abundant  than  those  of  the 
carnivora.  Animal  food,  however,  also  contains  elements 
which  long  resist  the  influence  of  the  digestive  juices :  thus 
the  horny  growths  of  the  epidermis  (hair,  nails,  etc.),  and 
the  yellow  or  elastic  tissues  (parts  of  tendons,  of  arterial 
coats,  etc.),  are  found  in  the  faeces  almost  entire. 


LARGE  INTESTINE.  'Ztl 

These  substances  are  carried,  by  slow,  peristaltic  contrac- 
tions, into  the  sigmoid  flexure.  Here  they  apparently  pause, 
and  are  carried  into  the  rectum,  in  an  intermittent  manner 
only,  under  the  influence  of  stronger  contractions;  they 
here  tend  to  produce  the  reflex  phenomenon  which  we  shall 
study  under  the  name  of  defecation:  if  this  attempt  at 
evacuation,  however,  does  not  succeed,  and  the  passage  is 
closed  to  them  the  faeces  return  to  the  sigmoid  flexure.  These 
movements  are  all  extremely  slow  and  of  such  a  character  as 
to  produce  considerable  compression  throughout  the  length 
of  the  lower  end  of  the  gut.  As  in  the  case  of  the  small 
intestine,  the  form  and  mode  of  production  of  these  move- 
ments are  not  yet  perfectly  known ;  they  are  peristaltiQ 
movements,  that  is,  movements  in  which  the  circular  tibres 
of  the  muscular  membrane  contract,  proceeding  in  a  down- 
ward direction,  causing  the  substances  to  pass  through  the 
intestinal  tube ;  thus  any  substance  being  compressed  above, 
is  forced  into  the  lower  part  of  the  intestine,  the  fibres  of 
which  are  still  relaxed.  Those  movements  called  anti- 
peristaltic^ which  take  place  in  the  contrary  direction,  and 
thus  have  the  efix^ct  of  forcing  back  the  contents  of  the  intes- 
tine, do  not  appear  to  exist  in  the  living  animal,  when  in  its 
normal  condition.^  They  are  evidently  produced  in  certain 
pathological  cases.  Those,  observed  in  the  intestinal  canal 
of  an  animal  in  which  the  abdomen  is  opened  immediately 
after  it  has  been  killed,  appear  to  be  owing  to  an  interruption 
in  the  abdominal  circulation,  causing  ultimate  excitation  of 
the  smooth  fibres,  at  the  instant  of  death.  We  have  scarcely 
any  means  of  deciding  on  the  nature  of  the  reflex  mechanism 
by  which  the  nervous  system  influences  or  produces  these 
movements.  The  solar  plexus  may,  perhaps,  serve  as  the 
centre  of  these  reflexes ;  embryology,  indeed,  shows  that 
this  abdominal  nerve  centre  appears  to  be  developed  inde- 
pendently of  the  spinal  cord.  The  solar  plexus  is,  however, 
united  to  the  cord  by  two  large  nerve  commissures,  if  they 
may  be  so  called,  the  pneumo-gastric  and  the  splanchnic 
nerves ;  it  is  remarkable  that  excitation  of  the  former  pro- 
duces or  increases  the  movements  in  the  intestines,  while 
excitation  of  the  latter  (great  splanchnic  nerves)  appears  to 
render  the  viscera  motionless,  and  paralyzes  their  muscular 

^  See  Braara-Honckgeest,  '*  Untersuchungen  iiber  Peristaltik 
des  Mageus  uud  Darmkanals.'*  (Pfliiger's  Archiv.,  September, 
1872.) 


278  DIGESTIVE  SYSTEM. 

walls.  The  splanchnic  nerves  are,  therefore,  to  the  intes- 
tines what  the  pneumo-gastric  nerve  is  to  the  heart,  that  Ib 
an  arresting  nerve  (Experiments  by  Pliuger). 

Onimus  and  Legros  studied  the  movements  of  the  differ- 
ent parts  of  the  digestive  canal  by  means  of  a  registering 
apparatus,  upon  wliich  a  lever  (set  in  motion  by  an  india- 
rubber  bag  introduced  into  the  intestinal  tube,  and  which 
set  in  action  its  contractions)  recorded  these  contractions  as 
they  occurred.  While  engaged  in  this  study,  they  observed 
that,  by  galvanizing  the  pneumo-gastric  nerve  by  means  of 
interrupted  currents,  the  movements  of  the  intestine  may  be 
checked,  and  checked,  not  when  in  a  state  of  contraction^  but 
when  e^itirely  relaxed.  "  In  this  case  a  veiy  remarkable 
depression  is  obtained  in  the  tracing,  and  it  is  important  to 
associate  the  fact  of  the  checking  of  the  lieart  in  diastole^ 
and  the  checking  of  the  respiratory  movements  in  inspira- 
tion^ during  the  excitation  of  the  pneumo-gastric  nerve  by 
interrupted  currents  "  (see  p.  40). 

It  is  easier  to  explain  what  goes  on  at  the  lower  extremity 
of  the  digestive  canal,  this  part  being  more  accessible,  and 
the  phenomenon  of  defecation  thus  becoming  perfectly  plain. 
First,  it  must  be  recollected  that  the  longitudinal  nmscular 
fibres  form  in  the  rectum  an  extremely  thick  and  powerful 
stratum,  and  that,  on  the  other  hand,  the  circular  fibres  are 
grouped  together  and  multiplied  in  such  a  manner  as  to  form 
a  sphincter  or  ring,  called  an  internal  sphincter^  formed  of 
smooth  muscular  fibres,  and  enclosed  in  another  and  more 
powerful  sphhicter,  called  the  external  sphijicter,  which  is 
formed  of  striated  fibres.  These  sphincters  do  not  exactly 
form  a  ring,  but  rather  an  antero-posterior  button-hole.,  con- 
fined by  two  muscular  bands,  which,  during  the  state  of 
repose,  are  quite  close  togetlier.  When  in  repose,  this 
sphincter,  by  virtue  of  its  elasticity  alone,  completely  closes 
the  opening  which  it  surrounds,  as  is  the  case  indeed  with  all 
the  sphincters  (see  Physiology  of  the  muscle,  natural  form 
of  the  muscle  and  sphincters  when  in  the  state  of  repose,  p. 
72).  These  contractions,  therefore,  are  no  more  permanent 
here  than  elsewhere :  the  ring-like  aperture  is  normally  oblit- 
erated by  the  natural  form  of  the  sphincter,  and  the  sphincter 
contracts  only  when  some  body  seeks  to  modify  its  form,  in 
order  to  dilate  the  orifice  which  it  surrounds.  Under  these 
circumstances  either  the  sphincter  does  not  react,  but  dilates 
readily,  on  account  of  its  great  elasticity,  and  the  passage 
takes  place ;  or  else  the  s|>hincter  reacts,  and  by  its  contrac- 


LARGE  INTESTINE.  279 

tion  closes  the  orifice  in  a  really  active  manner :  in  the  former 
of  these  two  cases  defecation  is  produced. 

Defecation  is  a  reflex  phenomenon  of  expulsion,  the  centre 
of  which  is  found  in  the  lower  part  of  the  cord,  as  is  proved 
by  pathological  cases.  At  the  beginning  of  this  reflex,  a 
vague  sensation  is  experienced,  which  can  hardly  be  defined, 
a  feeUng  of  weiglit  in  the  perineum  produced  by  the  presence 
of  the  faecal  matter.  The  seat  of  this  sensation,  the  desire^ 
is  in  the  rectum  only ;  in  the  other  parts  of  the  large  intes- 
tine these  substances  are  not  normally  felt.  In  cases  of 
artificial  anus,  however,  following  strangulated  hernia,  and 
having  their  seat  in  any  part  of  the  intestinal  tube,  it  has 
been  remarked  that  as  the  alvine  matters  approach  the  arti- 
fiicial  orifice  a  vague  sensation  is  felt,  resembling  that  of  the 
necessary  promptings  of  nature ;  which  seems  to  prove  that 
this  sensation  may  be  experienced  in  any  part  of  the  intes- 
tinal tube,  it  being,  perhaps,  only  due  to  the  weight  and 
pressure  of  the  faecal  substances  brought  together  in  a  mass 
(Bert).i 

Under  the  influence  of  this  feeling  a  series  of  expulsive 
efforts  are  made,  which  are  reflex,  as  we  have  said,  but  are 
under  the  influence  of  the  will,  either  by  increasing  their 
force  or  checking  them.  If  the  desire  is  not  satisfied,  an 
anti-peristaltic  movement  takes  place,  beginning  at  the  anal 
sphincter,  which  drives  the  excrement  back  into  the  sigmoid 
flexure,  whence,  after  a  time,  they  return  to  try  the  passage 
again.  If  this  attempt  be  resisted  several  times  in  succes- 
sion, the  rectum  at  length  loses  its  sensibility,  and  the  pres- 
ence of  the  excrement  ceases  to  give  rise  to  the  reflex  action 
which  we  are  about  to  study ;  this  is  the  cause  of  the  habitual 
constipation  of  persons  who  neglect  the  signs  mentioned,  and 
who  soon  find  themselves  obliged  by  artificial  means  (sup- 
positories) to  excite  the  dulled  sensibility  of  the  mucous 
membrane  of  the  rectum  and  of  the  nervous  fibres  which 
govern  the  centripetal  part  of  the  reflex. 

If  attention  is  paid  to  the  promptings  of  this  desire,  a 
reflex  contraction  of  the  muscular  walls  of  the  rectum  takes 
place  naturally ;  this  is  a  genuine  peristaltic  movement,  by 
means  of  which  the  excrement  is  discharged  into  the  anus, 
the  sphincter  of  which,  dilating  readily,  offers  no  resistance. 
If  the  Ibeces,  indeed,  are  in  an  abnormally  ffuid  state,  the 

'  See  Paul  Bert,  Art.  Defecation^  du  '*  Nouveau  Diet,  de  Mede- 
cine  et  de  Cbuurgie  Tratiques."     Vol.  X.,  p.  747. 


280  DIGESTIVE  SYSTEM. 

rectum  alone  can  expel  them,  without  tlie  will  having  any 
other  share  in  the  matter  than  that  of  not  offering  any 
obstacle  to  their  passage.  In  ordinary  cases,  however,  the 
soUd  state  of  tlie  excrement  requires  the  intervention  of 
more  numerous  and  considerable  forces,  which  act  principally 
under  the  influence  of  the  will :  the  first  is  the  phenomenon 
oi  straining,  by  means  of  which  the  larynx  closes,  causing  the 
walls  of  the  thoracic  cavity,  which  is  filled  with  air,  to  sup- 
ply a  fulcrum  to  the  muscles  which  are  about  to  act ;  all 
those  muscles  which  can  compress  the  abdomen,  that  is,  the 
muscles  of  the  abdominal  coat,  the  diaphragm,  and  the 
muscles  of  the  perineum  {levator  ani),  then  contract,  pro- 
ducing compression  on  every  side.  The  levator  ani,  while 
compressing  the  viscera  from  bottom  to  top,  brings  just  in 
front  of  the  excrement  the  orifice  through  which  it  must 
pass.  The  longitudinal  fibres  of  the  rectum,  which  are  so 
largely  developed,  act  for  the  same  purpose,  and  this  is  only 
one  mode  of  the  mechanism  which  we  studied  when  analyz- 
ing the  peristaltic  movement  (see  Deglutition,  p.  225).  More- 
over, these  longitudinal  fibres  terminate  below  by  folds, 
which  disappear  more  or  less  distinctly  in  the  perineum, 
forming  a  convex  curve  directed  towards  the  centre  of  the 
anus;  whence  it  follows  that  during  their  contraction  their 
curve  straightens,  and,  consequently,  dilates  the  oiifice 
through  which  the  excrement  is  to  pass. 


PART    SEYENTH. 

PULMONARY  MUCOUS  TISSUE.  — RESPIRATION. 
—  ANIMAL   HEAT. 

L    RESPIRATION. 


The  surface  of  the  respiratory  mucous^  is  that  which, 
next  to  the  epithelial  surftice  of  the  digestive  tract,  most 
readily  yields  to  interchanges  of  nutrition;  these  inter- 
changes are,  however,  in  the  normal  condition,  chiefly 
gaseous.  As  the  absorption  of  the  substances,  called  ali- 
mentary, occurs  slightly  over  all  the 
surfaces,  and  as  we  have  seen  that 
the  reabsorption  of  fat  happens  in  all  the 
tissues,  —  although  these  phenomena 
have  their  special  seat  at  the  level  of 
the  epithelium  of  the  digestive  tract, — 
so  the  gaseous  interchanges  take  place 
over  many  surfaces,  for  instance,  in 
ths  skin,  and  the  gases  mny  be  reab- 
sorbed in  the  most  interior  portion  of 
the  tissues  (as  in  sub-cutaneous  em- 
l)liysema) ;  yet  these  phenomena  are 
connected  chiefly,  in  the  superior  ani- 
mals, with  the  respiratory  mucous. 

The  respiratory  mucous  may,  from  an  embryological  point 
of  view,  be  considered  as  an  ottshoot  of  the  sub-diaplirag- 
matic  part  of  the  digestive  tract ;  indeed,  the  first  a])pearauce 
of  the  lungs  in  the  foetus  exhibits  the  form  of  a  growth  of 
the  epithelium,  of  the  anterior  wall  of  the  pharynx.     This 

^  It  may  have  been  noticed  that  the  word  ' '  mucous  ' '  has  been 
used  frequently  as  referring  to  the  mucous  coat,  tissue,  or  mem- 
brane. 


Fig.  72.  —Ramification  of  the 
pulmonary  poucli  in  tlie 
foetus  of  a  sheep,  length  one 
inch  and  a  hail{Mtlller), 


282 


PULMONARY  MUCOUS  TISSUE. 


offshoot,  which  is  at  first  solid,  becomes  hollow  and  bifur- 
cated as  it  is  developed  (Fig.  72) :  the  epithelium  at  the 
same  time  undergoes  a  change ;  from  having  been  pavement 
in  the  pharynx  it  becomes  columnar  and  vibratile  in  the 
pedicles  of  the  offshoots  (trachea  and  bronchi)^  and  pave- 
ment again  in  the  air  sacs  or  pouches  {alveoli).  Tlie  lungs 
may  thus  be  compared  to  a  gland,  the  pouches  of  which  are 


Fig.  73.  —  Larynx  of  a  man,  trachea,  bronchi,  and  lungs,  with  the  ramification 
of  the  bronchi  and  the  division  of  the  lunga  into  lobules.  (Dalton,"Humaa 
Physiology.") 

represented  by  the  alveoli  (Fig.  73),  and  the  excretory  tubes 
by  the  bronchi.  These  pouches  may  be  likened  to  a  conical 
and  pyriform  but  indented  organ,  the  summit  of  w^hich  is 
prolonged  by  a  bronchial  ramification :  this  ampulla  (Fig. 
74),  which  is  about  one-eighth  of  a  millimetre  in  diameter, 
has  not  a  simple  form,  but  is  uniformly  embossed  on  the  inside, 
where  it  presents  a  number  of  prominent  folds,  dividing  the 
primitive  alveolus  into  a  great  number  of  secondary  alveoli 


RESPIRATORY  MEMBRANE.  283 


m 

^H  or  vesicles  (Fig.  74,  c,  c).     The  alveoli  join  together,  forming 

^H  lobules^  which  are  easily  distinguished  on  the  surface  of  the 

^B  lung  in  a  system  of  network  (division  lines  of  the  lobules), 

^^B  and  the  lobules  themselves,  uniting,  form  the  lobes  of  the 


Fig.  74.  —Lobule  of  the  lung  in  man.* 

lung.  The  alveoli  are,  therefore,  very  numerous ;  their  num- 
ber has  been  estimated  approximately  as  seventeen  or  eighteen 
hundred  millions. 


I.    Structure  of  the  Respiratory  Membrane.  —  Arrange- 
ment OF  ITS  Parts. 

The  pulmonary  alveolus  constitutes  essentially  the  respir- 
atory surface :  it  consists  of  epithelium  and  a  substratum  of 
connective  tissue. 

1.  The  pulmonary  epithelium  is  formed  of  epithelial  layers, 
extremely  delicate  and  not  readily  observed,  arranged  in  a 
hingle  row,  and  frequently  at  a  considerable  distance  from 
each  other.^     In  the  normal  state  its  elements  exhibit  very 

1  See  Ch.  Schmidt,  *'  Do  I'Epithe'lium  Pulmonaire.'*  These  de 
Strasbourg,  1866,  No.  931. 

The  existence  of  the  pulmonary  epithelium  was,  for  a  long  time, 
disputed.  Villemin  was  one  of  its  most  ardent  opponents,  which 
is  not  to  be  wondered  at  when  we  consider  the  elaborate  process  of 

*  <7,  Termination  of  the  bronchial  tube,  h,  Cavity  of  the  lobule,  c,  c,  c,  c, 
Air-cells  or  vesicles.  (Dalton,  "  Human  Physiology.")  This  sac  or  pouch 
ftxactly  represents  the  whole  lung  of  a  frog. 


284 


PULMONARY  MUCOUS  TISSUE. 


few  metamorphoses  and  scarcely  any  epithelial  remains: 
they  even  show  a  tendency  to  waste  away  with  age ;  and  the 
walls  which  supported  them  also  falling  away,  what  is  called 

preparation  which  he  thought  necessary  for  the  study  of  the  pul- 
monary lobules  (desiccation,  bichloride  of  mercury,  water  of  am- 
monia, and,  finally,  iodine.  Now  the  pulmonary  epithelium  is  the 
most  delicate  of  all  the  tissues,  and  requires  the  same  process  of 
preparation  as  the  most  dehcate  epitheliums  of  the  serous  tissue. 
Elenz  (in  1864),  by  means  of  nitrate  of  silver,  ascertained  the 
existence  of  a  pulmonary  epithehum  in  all  the  vertebrated  animals, 
and  his  observations  have  been  since  confirmed  by  others.  Schmidt 
(op.  cit.),  by  employing  the  same  method,  arrived  at  the  following 


Fig.  75.  —  Pulmonaxy  epithelium.* 

conclusions;  in  the  mammalia  the  pulmonary  vesicles  of  the  em- 
bryo are  lined  with  regular  cells,  all  of  uniform  size;  in  the  new- 
born animals  some  of  these  cells  become  larger  and  cover  the 
capillaries,  while  the  rest  remain  unchanged,  united  together  in 
groups  in  the  meshes  of  the  capillaries  (Fig.  75).  Finally,  in 
adults  the  groups  consist  of  a  smaller  number  of  cells,  and  many 
of  them  are  quite  isolated.  The  large  cells  which  divide  them 
appear  to  be  partly  united,  resembling  membranous  layers,  ex- 
tremely simple  and  almost  amorphous. 

The  arguments  against  the  existence  of  the  pulmonary  epithe- 
lium which  have  been  drawn  from  the  study  of  comparative 
anatomy  have  all  proved  false  in  the  light  of  fuller  investigation. 
The  pond-loach  (cohitis  fossilis)  is  a  singular  fish,  which  swallows 

*  Ij  Capillan'-  vessels.  2,  Interstice  in  the  capillaries  (the  white  in  the  dia- 
gram IS  a  portion  of  the  capillary  network;  the  dotted  lines  represent  the 
meshes  or  interstices  of  this  network).  3,  Outline  of  the  epithelial  cells. 
4,  Nuclei  of  the  cells,  usually  found  in  a  mesh. 


RESPIRATORY  MEMBRANE.  285 

pulmonary  emphysema  ensues,  a  change  which  is  so  often 
observed  in  old  people.  This  is  not  the  case,  however,  in 
pathological  conditions:  when  irritated,  this  epithelium  be- 
comes hypertrophied  and  proliferates.  This  is  what  gives  " 
rise  to  the  false  membranes  in  croup,  and  to  the  characteris- 
tic features  of  pneumonia;  the  alveoli  are  then  entirely- 
obliterated  and  transformed  into  a  compact  and  resisting 
tissue,  for  which  reason  this  state  is  known  by  the  name  of 
hepatisation.  This  epithelium  has  also  the  chief  share  in 
producing  tubercle^  and  some  other  less  common  transforma- 
tions, as  cancer  of  the  lung. 

In  cases  of  infarctus  of  the  lung,  especially  when  pro- 
duced artificially  in  the  dog,  the  epithelium  may  easily  be 
seen  to  have  undergone  a  certain  hypertrophy  in  the  pul- 
monary alveoli,  infiltrated  with  blood,  some  of  its  cells  falling 
into  the  alveolus,  and  mixing  with  the  blood  globules  (Vul- 
pian). 

2.  This  epithelium  is  supported  by  a  m.emhrane^  which 
forms  a  sort  of  shell  to  the  alveolus.  This  consists  of  a  con- 
nective tissue,  which  is  nearly  amorphous  and  full  of  plasmatic 
cells,  and  it  has  a  large  number  of  elastic  fibres,  forming  a 
close  network,  the  meshes  of  which  are  extremely  minute. 
Sorrietimes  the  elastic  fibres  are  found  at  a  greater  distance 
from  each  other,  and,  by  dividing  them,  they  may  be  made 
perfectly  distinct  in  a  preparation.  These  elastic  elements, 
formed  of  fibres  whose  outline  is  strongly  marked  with  nu- 
merous bifuications,  are  of  great  importance  in  a  physiological 
point  of  view;  as,  for  instance,  in  sputa,  these  resist  decay 
for  a  long  time,  and  are  often  the  only  part  of  a  necrosed  and 
worn-out  lung,  which  preserves  the  characteristic  features  that 
can  be  recognized  by  the  microscope.  In  some  animals  this 
membrane  is  composed,  in  part,  of  smooth  muscular  fibres :  it 
is  not  easy  to  decide,  by  anatomical  examination,  whether 
the  case  is  the  same  in  man.^     We  shall  inquire  later  whether 

air  by  the  mouth,  and,  after  having  absorbed  a  part  of  the  oxygen, 
gives  off  carbonic  acid  by  the  anus.  Leydig  could  discover  no 
intestinal  epithelium  in  this  fish,  in  -which  the  respiration  is  partly 
intestinal;  but  Schmidt,  by  the  aid  of  nitrate  of  silver,  ascertained 
that  the  surface  in  question  has  a  complete  epithelial  covering: 
here,  too,  the  different  cells  are  intermingled  without  any  order, 
being  sometimes  of  equal  size  and  tolerably  regular  in  arrange- 
ment, and  at  others  grouped  in  such  a  manner  that  several  small 
cells  appear  surrounded  by  smaller  ones. 

'  "  The  muscular  fibres  appear  in  the  large  bronchi  under  the 


286  PULMONARY  MUCOUS  TISSUE. 

this  question  can  be  solved  by  physiological  experiments. 
This  membrane  is  especially  characterized  by  the  large  num- 
ber of  blood-A^essels,  consisting  of  a  network  of  extremely 
small  capillaries,  so  small  as  to  allow  only  of  the  passage  of 
a  blood  globule,  and  placed  very  close  together,  the  meshes 
which  separate  them  being  exceedingly  fine.  It  is  found,  for 
instance,  that  on  a  given  surface  of  a  pulmonary  alveolus  the 
space  occupied  by  the  capillaries  amounts  to  three-fourths 
of  the  surface,  and  the  intervals  between  them  to  only  one- 
fourth.  As  the  entire  surface  occupied  by  the  alveoli  amounts 
to  two  hundred  square  metres,  it  follows  that  the  capillaries 
form  an  area  of  160  square  metres.  This  network  is  exceed- 
ingly fine  and  delicate,  being  only  about  the  thickness  of  a 
blood  globule ;  it  nevertheless  contains  nearly  two  litres  of 
blood.  It  has  also  been  calculated  that  in  twenty-four  hours 
at  least  two  thousand  litres  of  blood  pass  through  it ;  this 
network  is  thus  continually  renewed.  These  figures  are 
important,  as  enabling  us  to  form  some  idea  of  the  magni- 
tude of  the  gaseous  exchanges  which,  we  shall  see,  take 
place  between  the  blood  and  the  volume  of  air  with  which 
it  is  brought  nearly  in  contact,  being  separated  only  by  the 
thin  wall  of  the  capillaries  and  an  extremely  delicate  epithe- 
lium. 

We  must,  therefore,  study  the  mechanism  by  means  of 
which  the  external  air  is  brought  in  contact  with  the  respir- 
atory surface,  and  see  how  it  is  renewed  after  the  diffusion 
of  gas  between  this  surface  and  the  blood  has  taken  place. 

These  phenomena  in  every  way  resemble  those  of  the 
digestion;  but  while  the  food  received  into  the  digestive 
tube  must,  before  it  can  be  assimilated,  undergo  a  number 
of  metamorphoses,  the  respiratory  elements  of  the  air  are 
assimilated  at  once.  The  air  simply  undergoes  a  slight 
preparatory  process,  which  brings  it  to  the  same  state  of 
temperature  and  of  humidity  as  the  pulmonary  surface  with 
which  it  is  to  come  in  contact.  The  origin  of  the  pulmonary 
tree  is  so  arranged  as  to  render  it  inevitable  that  the  air 
should    undergo    this    slight    modification :    for   the   nasal 

form  of  flattened,  circular  groups  ;  these  groups  form  a  complete 
layer.  As  they  are  also  found  in  branches  of  a  size  from  0™.  22 
to  O^i.  18,  they  probably  extend  to  the  pulmonary  lobules."  (Kol- 
liker,  1870). 

This  opinion  as  to  the  presence  of  the  muscular  element  in  the 
coat  of  the  pulmonary  vesicles  was  upheld  by  Moleschott,  Fiso- 
Bonne,  Hirschmann,  and  Chrzonszczewsky. 


MECHANICAL  PHENOMENA    OF  RESPIRATION.      287 

chambers  are  lined  by  an  extremely  moist  mucous  membrane, 
containing  a  large  quantity  of  blood,  and  consequently  very 
warm ;  it  covers  a  number  of  folds  (turbinated  or  spongy 
bones)  in  passages  (meatus),  through  which  the  air,  as  it 
I3asses,  is  filtered,  simultaneously  becoming  charged  with 
moist  vapor,  and  being  brought  to  the  temperature  of  the  body. 
These  considerations  alone  prove  that  respiration  is  naturally 
performed  through  the  nose,  and  not  through  the  mouth,  and 
show  the  danger  of  breathing  through  the  latter  when  in  a 
cold  dry  atmosphere. 

II.   Mechanical  Phenomena  of  Respiration. 

The  best  method  of  exhibiting  the  arrangement  of  the 
circulating  reservoir  was  presented  by  a  diagram,  and  we 
shall  find  this  plan  equally  useful  in  regard  to  the  respiratory 
system.  We  see,  in  this  way,  that  the  air-bearing  tubes, 
being  placed  side  by  side  and  the  partitions  left  out,  repre- 
sent a  very  wide  cone,  having  for 
its  base  the  alveolar  surface  which 
we  have  already  studied,  and  for 
its  summit  the  opening  of  the 
nasal  chambers  (Fig.  76). 

This  arrangement  shows  us 
that  when  the  air,  no  matter  by 
whatever  mechanism,  enters  or 
leaves  this  reservoir,  the  velocity 
of  its  current  will  be  very  differ- 
ent in  the  different  zones  of  the   ^.  ,  ^J'^s  '^^• 

,     .  .  ,  ^ ,        Diagram  of  the  pulmonary  cone.* 

cone,  being  more   rapid   as  the 

zone  is  narrower  (higher),  and  slower  as  the  zone  is  wider 
(nearer  the  base) ;  and  that  at  the  base  of  the  cone,  on  the 
surfjxce  of  the  alveoli,  the  air  is  comparatively  stagnant.  In 
spite  of  the  number  of  our  respiratory  movements,  the  air  at 
the  level  of  the  breathing  surface  (alveolar)  is  never  found 
pure,  but  contains  as  much  as  8  per  cent  of  carbonic  acid, 
produced  by  former  gaseous  exchanges.^     The  upper  part  of 

*  The  figure  8  per  cent  may  appear  too  high,  and  yet  there  is 
no  doubt  that  it  is  below  the  truth.  Grehant  made  it  7.5  per  cent 
by  direct  experiment,  but  he  did  not  analyze  the  gas  which  is  in 
immediate  contact  with  the  respiratory  surface;   because,  as  we 

*  T,  Trachea.  P,  Cavity  of  the  lung.  E,  E,  Respiratory  surface  (pavement 
epithelium  of  the  alveoli. 


288  PULMONARY  MUCOUS  TISSl 

the  cone  contains  air  nearly  resembling  atmospheric  air :  the 
air  in  the  middle  zones  is  less  pure  than  this,  but  less  degen- 
erated than  tlie  first,  containing  only  yA^  of  carbonic  acid.^ 
Thus  it  rarely  happens  that  the  respiratory  blood  network 
comes  in  direct  contact  with  ordinary  atmospheric  air. 

Grehant,  replacing  atmospheric  air  by  hydrogen,  succeeded 
in  determining  how  many  respiratory  movements  are  neces- 
sary for  the  gas  and  the  former  contents  of  the  lung  to  be  so 
mingled,  as  to  become  homogeneous.  These  experiments 
show  that  at  least  four  or  five  successive  respiratoiy  move- 
ments are  required  to  renew  the  gas  contained  in  the  pul- 
monary cone.  By  giving  a  certain  quantity  of  hydrogen  to 
a  person  to  breathe,  and  then,  in  a  series  of  experiments, 
analyzing  the  gas  from  the  first,  second,  and  third  expiration, 
etc.,  Grehant  found  that  it  is  generally  only  after  five  inspir- 
ations and  expirations,  made  in  a  receiver  full  of  hydrogen, 
that  this  gas  is  uniformly  spread  throughout  the  lung.  These 
experiments  are  extremely  exact,  for  the  blood  scarcely 
absorbs  any  hydrogen  (the  difference  made  by  absorption 
being  scarcely  2V)  • 

The  introduction  of  air  into  the  respiratory  cone  and  its 
expulsion  take  place  by  means  of  the  respiratory  move- 
ments of  inhalation  and  exhalation. 

A.  Inhalation. 

The  movement,  by  means  of  which  inhalation  takes  place, 
consists  in  increasing  the  distance  between  the  base  and  the 

shall  see  later,  this  gas  cannot  be  exhaled,  the  lung  being  never 
entirely  empty:  he  analyzed  those  layers  only  which  precede  the 
one  in  question,  and  we  may  therefore  infer  that  the  proportion  of 
carbonic  acid  in  this  latter  must  equal  or  even  exceed  8  or  9  per  cent. 
Grehant's  experiment  is  as  follows:  500  cubic  cent,  of  hydrogen 
are  inhaled,  and  then  immediately  two  exhalations  are  made,  the 
second  into  a  small  india-rubber  bag,  furnished  with  a  stop-cock, 
from  which  the  air  is  entirely  excluded  by  compression  and  by  the 
presence  of  a  small  quantity  of  hydrogen,  previously  introduced. 
If  the  gas  collected  in  this  bag  be  analyzed,  as  the  hydrogen  is 
replaced  by  common  air,  it  is  found  to  contain  7.5  per  cent  of  car- 
bonic acid,  13.5  of  oxygen,  and  78.6  of  nitrogen. 

1  Becher  and  Holmgren,  by  sounding  the  lung  with  a  probe, 
extracted  the  air  from  the  bronchi  (middle  zones  of  the  pulmonary 
cone),  and  found  it  to  contain  carbonic  acid  in  the  proportion  of 
2.3  per  cent.  (See  T.  Strauss,  '*  Des  Travaux  Recents  sur  les  Gaz 
du  Sang  et  les  Echanges  Respiratoires."  (Archiv.  Gener.  de 
Medecine,  1873.) 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      289 

summit,  and  also  enlarging  the  other  dimensions  of  the  cone 
by  separating  its  walls  and  pulling  out  the  surface  of  the 
base.  This  produces  a  difference  between  the  pressure  of 
the  exterior  air  and  that  in  the  respiratory  cone,  and  also 
between  that  of  the  different  layers  of  air  in  this  cone,  caus- 
ing the  interior  and  exterior  gases  to  mingle  more  closely 
together. 

This  dilatation  of  the  pulmonary  cone  takes  place  by 
means  of  the  cage  of  the  thorax^  of  which  the  diameter  is 
increased  by  the  contraction  of  the  muscles  and  by  the 
working  of  the  bony  levers  of  which  it  is  formed.  The  wall 
of  the  thorax  is  composed  in  front  and  at  the  sides  of  the 
sternum  and  the  ribs,  and  of  the  diaphragm  below. 

The  ribs  are  bo7iy  arches.^  sloping  from  top  to  bottom,  from 
back  to  front,  and  from  within  to  without ;  so  that  when  they 
rise,  having  as  a  fixed  point  their  posterior  extremity  (costo- 
vertebral articulation),  their  an- 
terior extremity  is  thrown  for- 
ward, and  their  external  convex- 
ity thrown  outwards,  causing  an 
increase  in  the  antero-posterior 
and  transverse  diameter  of  the 
lung:  the  Fig.  77  will  better 
illustrate  this  mechanism  than 
any  explanation.  The  sternum 
must  obviously  move  freely 
away  from  the  vertebral  col- 
umn :  the  sternum  and  the 
vertebral  column,  being  joined 
by  the  ribs,  form,  as  it  were,  the 
two  supports  of  a  ladder  with 
oblique  rounds,  and  as  these 
rounds  become  horizontal,  the 
distance  between  the  two  sup- 
ports increases;  the  forcible 
dilator  of  the  urethra  employed 
by  surgeons  constitutes  a  simi- 
lar apparatus.     Finally,  the  in-         ™     „     ,^       . 

v        ]       ^  n  3    1    \.i_         -1  Pig.  77.  —  Thoracic  cage* 

clmed  plane  formed  by  the  rib 

sloping  downwards  and  outwards,  turns  as  it  rises,  about  an 

oblique   axis   extending  from  the  sternum  to  the  vertebral 

*  Vertebral  column,  with  the  ribs  attached  (dorsal  region).  These  ribs  ex- 
tend to  the  front,  where  they  join  the  sternum  (directly,  in  the  case  of  the  seven 
upper  ribs). 

19 


290  PULMONARY  MUCOUS  TISSUE. 

column,  and  representing  the  cord  of  the  bow  formed  by  the 
rib :  the  convexity  of  the  rib  is  thus  turned  outwards,  causing 
a  transverse  dilatation  of  the  thorax. 

The  muscles  which  communicate  these  motions  to  the  ribs 
are  well  known ;  they  are  those  of  the  walls  of  the  thorax, 
and  their  action  is  demonstrated  by  simply  studying  the 
direction  of  their  fibres.  They  do  not  always  act,  however. 
When  the  breathing  is  calm,  as  it  usually  is,  contraction  of 
the  intercostals,  the  scaleni,  and,  perhaps,  a  portion  of  the 
senatus  magnus  and  of  the  serratus  posticus  superior,  etc., 
will  suffice ;  but,  if  the  inspiration  becomes  forcible,  and,  as 
it  were,  constrained,  we  find  (in  cases  of  dyspnoea,  for  in- 
stance) that  the  sterno-cleido-mastoideus,  the  pectoral,  the 
latissimus  dorsi,  and  those  muscles  in  general  which,  acting 
from  a  fixed  position  (especially  when  the  arms  are  elevated 
and  fixed)  serve  to  raise  the  ribs  and  the  sternum ;  all  these 
come  in  play  as  re-enforcements.  We  shall  also  see  that  the 
diaphragm  even  may  assist  in  the  elevation  of  the  ribs. 

The  working  of  these  muscles  may  be  easily  observed  in 
a  single  anatomical  inspection.  This  is  not  the  case,  how- 
ever, with  the  intercostal  muscles^  which  have  always  been  a 
subject  of  keen  discussion  among  physiologists.  We  know 
that  these  muscles  are  divided  into  internal  intercostal  and 
external  intercostal  muscles,  the  fibres  of  each  arranged  cross- 
wise. Every  possible  suggestion  has  been  made  as  to  the 
mode  of  action  of  these  muscles,  which  have  been  thought 
to  possess  the  power  of  inspiration  and  expiration,  or  one  or 
the  other  only.^     To  our  mind,  the  intercostal  muscles  per- 

^  Beau  and  Maissiat  (Archives  G^ndrales  de  Medecine,  1842, 
1843)  have  drawn  up  a  curious  fist  of  the  theories  entertained  as 
to  the  functions  of  the  intercostal  muscles.  The  ten  theories  have 
each  been  defended  by  numerous  physiologists  from  Hamberger  and 
Haller  to  Beau,  Maissiat,  and  Sibson  Since  that  time  (184:)) 
other  physiologists  have  taken  part  in  this  still  undecided  and 
apparently  fruitless  discussion.  These  theories  may  be  summed 
up,  by  dividing  them,  as  is  done  by  Sappey,  into  six  classes: 
1.  The  external  and  internal  intercostal  muscles  are  both  inspiratory : 
Borelli,  Senac,  Boerhaave,  Winslow,  Haller,  Cuvier,  Ducheune  (de 
Boulogne),  Marcellin  Duval.  The  latter  bases  his  opinion  on  ex- 
periments made  on  executed  criminals  a  short  time  after  death, 
when  the  muscles  were  still  excitable.  Duchenne  (de  Boulogne) 
rests  chiefly  on  clinical  observations  made  in  cases  of  paralysis,  in 
which  respiration  was  kept  up,  in  spite  of  the  respiratory  muscles 
being  paralyzed,  showing  that  active  inspiration  must  have  taken 
place  by  means  of  the  intercostal  muscles.     We  remark,  in  all  the 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      291 

form  neither  of  these  two  functions:  their  principal  office 
being  to  complete  the  wall  of  the  thorax  by  filling  up  the 
intercostal  spaces.     It  may  be  asked,  however,  if  this  could 

cas(is  of  progressive  atrophy  reported  by  Duchenne,  that  no  men- 
tion is  made  of  the  levatores  costarum  (surcostaux) ,  a  subject  on 
which  physiologists  disagree  as  much  as  on  that  of  the  intercostals. 
Duchenne  gives  no  opinion  either  way,  and  it  appears  probable 
that  we  shall  be  right  in  supposing  the  continuance  of  respiration 
to  be  due  to  the  persistence  of  these  muscles.     2.    They  are  both 
expiratory:  Vesalius,  Diemerbrock,  Sabatier.     This  is  the  opinion 
held  by  Beau  and  Maissiat :   according  to  them  the  intercostal 
muscles  come  in  play,  especially  when  complex  expiration  takes 
place  (as  in  screaming  or  coughing) ;  at  such  times,  in  vivisection, 
the  fibres  of  these  muscles  straighten  and  become  tense,  while  in  inspi- 
ration they  are  depressed  and  look  inwards  towards  the  lung.   These 
physiologists  adduce,  in  favor  of  their  theory,  an  argument  drawn 
from  comparative  physiology:  "  The  respiration  of  birds  is  known 
to  differ  from  that  of  the  mammalia;  expiration  in  birds  is  the 
active,  and  inspiration  only  the  passive,  result  of  the  elasticity  of 
the  ribs,  which  spread  apart,  after  having  been  pressed  together  by 
the  action  of  the  expiratory  muscles.     Consequently,  the  intercos- 
tal muscles,  which  exist  in  birds  as  well  as  in  the  mammifera,  are 
affected  only  in  expiration.     We  cannot  beheve  that  those  muscles 
which  are  expiratory  in  birds  are  inspiratory  in  the  mammifera." 
3.    The  external  intercostal  muscles  are  expiratory^  and  the  internal 
inspiratory :  Galien,  Bartholin.     4.    The  external  intercostal  muscles 
are    inspiratory,    and    the    internal    expiratory:     Spigel,    Vesling, 
Ilamberger.     This    opinion  is  principally  founded  on  study  of 
Hamberger's  diagram  (see   Fig.   78,  and  his  explanation,  given 
in  the  text).     It  has  been  somewhat  modified  by  Sibson:  "  The 
external  intercostal  between  the  thoracic  set  of  ribs  are  through- 
out   inspiratory  ;    those    portions    between    their    cartilages    are 
expiratory,    between    the    diaphragmatic    set    of    ribs    they  are 
iiisjyii'utory   lehind,   expiratory  at   the  side  and  in  front,  and  be- 
tvveiin  their  cartilages  they  are  inspiratory  ;   between  the  inter- 
mediate set  of  ribs  they  are  for  the  most  part  slightly  inspiratory 
between  the  ribs,  and  expiratory  in  front  between  ithe  cartilages." 
(''  Mechanism  of  Respiration:  Philosophical  Transactions,"  1847). 
Though  this  theory  seems  to  involve  us  in  confusion  and  trifling 
distinctions,  if  considered  in  a  general  point  of  view,  we  shall  find, 
with  Hermann,  that  it  leads  to  a  simpler  conception  than  at  first 
appears:  "  The  external  muscles  are  inspiratory  in  the  bony  parts 
of  the  ribs,  and  the  internal  in  the  cartilaginous.     As^  however^ 
this  is  almost  the  chief  action  of  the  two  directions  of  the  fibres^  the 
intercostal  may,  in  general,  he  classed  among  the  inspiratory  muscles  " 
(Hermann).     5.    The  external  and  internal  intercostal  are  at  once 
inspiratory  and  expiratory :  Mayow,  Magendie.     6.    The  two  inter- 
costal muscles  are  passive  in  the  movements  of  inspiration  and  expira- 


292  PULMONARY  MUCOUS  TISSUE. 

not  be  done  as  well  by  the  fibrous  tissue.  The  presence  of 
the  muscular  tissue  is  explained,  if  we  remember  the  general 
properties  of  muscle,  which  is  the  most  elastic  tissue  of 
the  whole  economy.  In  this  case  a  tissue  of  peculiar  elas- 
ticity is  required,  the  dimensions  of  the  intercostal  spaces 
changing  incessantly  in  movements  of  the  thorax.  A  tissue 
was  required  which  would  remain  tense  between  the  ribs, 
which  would  not  be  depressed  from  without  inwards  by  exte- 
rior pressure  during  inspiration,  or  from  within  outwards  by 
intrapulmonary  pressure  during  expiration.  This  function  is 
so  important  that,  in  order  to  fulfil  it,  the  elasticity  of  the 
muscular  tissue  of  the  intercostal  muscles  must  be  kept  in 
constant  repair  by  nutrition ;  for  instance,  if,  in  pleuritis, 
inflammation  has  extended  to  these  muscles,  they  become 
powerless  to  perform  their  appointed  function,  and  in  such 
cases  an  autopsy  shows  the  lungs  transversely  grooved, 
having  received  this  impression  from  the  intercostal  spaces, 
which  then  become  capable  of  making  this  depression. 

The  necessity  of  preserving  a  constant  elasticity  of  the 
intercostal  spaces  explains,  finally,  the  existence  of  two  layers 
of  muscles,  the  external  and  the  internal  intercostal  muscles. 
A  simple  diagram  of  the  direction  of  these  muscles  (called 
Hamberger's  diagram.  Fig.  78)  shows  that,  as  the  ribs  de- 
scend (in  expiration),  the  distance  between  the  j^oints  of 
insertion  of  the  intercostal  muscles  increases ;  and,  again, 
diminishes  as  they  rise  (in  inspiration)  :  the  reverse  takes 
place  in  the  case  of  the  internal  intercostal  muscles.  From 
this  fact  conclusions  have  been  drawn  as  to  the  effect  pro- 
duced by  the  contraction  of  these  muscles,  the  external 
being  considered  as  elevating  or  inspiratory  muscles,  and  the 
internal  as  depressing  or  expiratory  (Hambeiger).  This 
diagram  may  be  more  clearly  explained,  however,  it  seems 
to  us,  by  saying  that  the  elasticity  of  the  external  intercostal 
muscles  is  brought  into  play  during  expiration,  and  that  of 
the  internal  intercostal  during  inspiration.  This  alternation 
of  elasticity  in  the  wall  is  quite  indispensable ;  because,  in 
inspiration  it  is  depressed   from  without  inwards,  and  in 


tion^  and  perform  the  office  of  a  resisting  wall:  Van  Helmont, 
Arantius,  Cruveilhier:  rather,  they  contract,  not  to  produce  the 
movements  of  inspiration  and  expiration,  but  in  order,  when  they 
do  occur,  to  resist  the  pressure  of  either  the  exterior  or  interior 
air  (KiJss).  (See  Aug.  Jobelin,  "  Etude  Critique  sur  les  Muscles 
Intcrcostaux."     These  de  Strasbourg,  1870,  No.  287.) 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      293 


Fig.  78. 
Diagram  of  the  intercostal  muscles.* 


expiration  from  within  outwards.  We  can  also  understand 
how,  in  violent  efforts  of  respiration  these  muscles  contract, 
not,  however,  in  order  to  move 
the  ribs,  but  to  support  the 
thoracic  wall  which  their  elas- 
ticity alone  would  be  powerless 
to  keep  tense  the  spaces  between 
the  bony  arches.  Hamberger's 
diagram,  in  this  point  of  view, 
shows  contraction  of  the  exter- 
nal intercostal  muscles  during 
inspiration,  and  of  the  internal 
during  expiration. 

The  intercostal  spaces  are  not 
the  only  part  of  the  thoracic 
wall  in  which  the  muscular  ele- 
ments are  so  arranged  as  to 
resist  the  changes  of  form  in- 
duced by  variations  in  pressure :  in  forcible  inspirations, 
depressions,  supra-sternal  or  supra-clavicular  depression^ 
are  produced  at  the  summit  of  the  thoracic  cage,  the  base 
of  the  neck.  It  is  in  these  very  parts  that  we  find  muscular 
layers  (subcutaneous)  or  muscular  bands  (omohyoid)  leading 
from  the  aponeuroses,  and  thus  resisting  the  pressure  from 
without  inwards,  especially  in  yawning,  sobbing,  etc. 

We  see,  in  short,  that  the  transverse  and  antero-posterior 
diameters  of  the  chest  are  increased  by  the  play  of  the  costal 
arches,  set  in  motion  by  the  contraction  of  a  great  number 
of  muscles,  some  of  which  are  constantly  in  play,  while  others 
are  only  accessory,  and  made  use  of  in  cases  demanding 
extraordinary  power ;  other  muscles,  the  intercostal,  in  par- 
ticular, serve  only  to  keep  the  walls  of  the  thorax  in  shape : 
in  normal  respiration  their  elastic  properties  alone  suffice  to 
produce  this  effect,  but  their  contraction  is  necessary  in 
labored  breathing. 

The  enlargement  of  the  vertical  diameter  is  accomplished 
by  means  of  the  diaphragm.  This  muscle  forms  the  base 
of  the  thoracic  cone,  and,  as  this  descends,  considerably 
modifies  the  capacity  of  the  cone :  its  action  exactly  resem- 


*  Diagram  known  as  Hamberger's. 

C  C,  D  C7,  Ribs  raised.  C  D,  D  D',  Ribs  lowered.  I V,  Internal  intercostal 
muscles,  extended  when  the  ribs  are  raised  (I),  and  relaxed  when  the  ribs  are 
lowered  (F).  E  C,  External  intercostal  muscles,  extended  when  the  ribs  axH 
lowered  (£'),  and  relaxed  when  the  ribs  are  raised  (E). 


294  PULMONARY  MUCOUS  TISSUE. 

bles  that  of  a  piston  in  the  cylinder  of  a  pump.  This 
muscle,  it  is  true,  has  the  form  of  an  arch,  and  it  has  been 
thought  that  in  contraction  its  curve  is  straightened,  and,  in 
this  way,  enlarges  the  vertical  diameter  ot  the  cavity  of 
which  it  forms  the  base.  This  base  is  represented  to  be 
convex  upwards  during  the  repose  of  the  muscle,  and 
flat  during  its  contraction.  It  must,  however,  be  remarked 
that  the  curvature  of  the  diaphragm  exactly  coincides  with 
that  of  the  abdominal  viscera,  as,  for  example,  on  the  right, 
with  that  of  the  liver ;  thus,  when  the  muscle  contracts,  it 
has  no  power  to  modify  this  convexity  or  curve,  but  can 
only  cause  it  to  change  its  place  from  top  to  bottom,  driving 
the  viscera  before  it  in  the  same  direction ;  thus  we  see  the 
abdominal  walls  rise  synchronically  with  each  inspiratory 
dilatation  of  the  thorax.  The  diaphragm  thus  constitutes  a 
piston  having  a  convex  form^  working  in  the  cylinder  of  a 
pump  formed  by  the  thoracic  cage;  in  descending,  however, 
it  does  not  act  only  on  the  vertical  diameter  of  the  thorax. 
We  must  remember  that  its  circular  edge  is  inserted  in  the 
ribs,  that  these  latter  are  movable,  and  that,  consequently, 
when  the  arched  centre  of  the  diaphragm  is  directed  down- 
wards^ its  circular  edge  is  sensibly  elevated;  in  other  words, 
this  muscle,  like  many  others,  has  no  really  fixed  points  of 
insertion,  and  its  fibres,  as  they  contract,  present  at  one  time 
a  relatively  fixed  point  on  the  ribs,  in  order  to  lower  both 
the  phrenic  centre  and  the  viscera,  and  on  the  viscera 
(phrenic  centre),  in  order  to  raise  the  ribs  and  the  sternum. 

By  this  action  the  diaphragm  forces  the  ribs  forward  and 
outward,  and,  at  the  same  thne,  dilates  the  thorax  in  its 
antero-posterior  and  transverse  diameters ;  it  may,  therefore, 
be  said  to  act  at  once  on  the  three  diameters  of  the  chest. 
Most  of  the  movements  made  in  inspiration,  especially  in 
young  subjects  and  in  man,^  proceed  from  the  diaphragm ; 
women,  after  attaining  the  age  of  puberty,  form  an  exception 
to  this  rule,  the  respiratory  type,  instead  of  being  abdominal 
(diaphragmatic)  or  costo-inferior.,  being  rather  costo-superior. 
This  fact  has,  no  doubt,  some  connection  with  the  genital 

1  Paralysis  of  the  diaphragm  causes  the  greatest  possible  de- 
rangement in  all  those  functions  which  require  that  the  thoracic 
cage  should  be  in  perfect  working  order;  although  phonation  is  not 
destroyed,  the  voice  becomes  extremely  weak ;  coughing  and  sneez- 
ing greatly  hinder  respiration.  (See  Duchenne  (of  Boulogne), 
*'  De  r Electrisation  Localisde."     Paris,  1872,  p.  908  ) 


MECHANieAL   PHENOMENA   OF  RESPIRATION.      295 

functions  at  the  time  of  gestation,  as  the  diaphragm  could 
not  then,  without  injury,  press  upon  the  gravid  uterus. 

In  short,  in  inspiration  the  thorax  is  dilated  in  every  direc- 
tion, the  action  of  the  diaphragm  serving  chiefly  to  produce 
this  effect.  In  making  the  complete  inspiration  which  is 
necessary  when  some  extraordinary  effort  is  demanded,  all 
the  inspiratory  powers,  and  all  the  mobility  of  which  the  ribs 
are  capable,  are  brought  into  activity ;  the  sternum  is  also 
raised  by  the  muscles  inserted  at  its  upper  extremity.  But, 
under  ordinary  circumstances,  when  the  breathing  is  quiet 
and  unconsciously  performed,  it  is  found  that,  in  the  same 
person,  some  of  the  ribs  possess  an  extraordinary  freedom  of 
movement,  while  others  are  nearly  motionless,  and  that  in 
the  case  of  different  persons,  under  similar  conditions,  the 
same  ribs  are  not  always  found  to  be  influenced  by  movements 
of  the  greatest  extent.  In  some  cases,  also,  the  whole 
thoracic  cage  seems  nearly  motionless,  no  movement  of  the 
ribs  can  be  detected.  These  facts  have  led  to  the  establish- 
ment of  three  types  of  respiration  (Beau  and  Maissiat)  :  the 
abdominal  type,  the  costo-inferior  type,  and  the  costo-supe- 
rior.  In  children,  of  both  sexes,  respiration  is  abdominal 
(see  above);  in  man,  it  is  costo-inferior/  in  woman,  it  is 
generally  costo-superior.  This  distinction,  however,  must 
not  be  looked  upon  as  absolute :  the  diaphragm,  even  when 
it  acts  alone,  evidently  raises  the  lower  ribs;  in  the  costo- 
superior  type,  on  the  other  hand,  the  lower  ribs  are  also 
elevated  to  a  certain  degree,  the  sternum  being  unable  to 
move  without  drawing  them  as  it  rises. 

What  is  the  state  of  the  lungs  during  these  movements  in 
the  thorax?  We  have  seTen  that  the  pulmonary  cone  com- 
municates with  the  exterior  air:  between  the  external  surface 
of  the  lung  and  the  internal  surface  of  the  cavity  of  the 
thorax,  however,  there  exists  a  cavity,  entirely  closed,  which 
is  called  the  pleural  cavity.  By  means  of  this  empty  space, 
the  lung  adheres  to  the  cage  of  the  thorax,  and  follows  its 
every  movement,  exactly  as  a  stone  to  which  a  piece  of 
moistened  leather  is  fastened  by  suction,  follows  the  leather, 
when  it  is  lifted  up:  this  well  known  child's  toy,  exactly 
represents  tlie  mechanism,  by  means  of  which  the  thoracic 
cone,  being  actively  enlarged,  forces  the  pulmonary  cone  to 
follow  all  its  changes  in  size,  and,  in  short,  to  dilate.  This  is 
the  mechanism  of  inspiration :  the  lung  is  quite  passive ;  the 
thoracic  cage  dilates  actively,  and  the  lung  is  obliged  to 
follow  suit. 


296  PULMONARY  MUCOUS  TISSUE. 

The  effect  of  this  mechanical  phenomenon  is  to  introduce 
a  certain  quantity  of  air  into  the  lung.  Indeed,  the  principle 
which  governs  the  movements  of  the  gases  in  respiration  is 
the  same  as  that  which  regulates  the  cii-culation  of  the  fluids ; 
that  is  to  say,  the  consequence  of  inequality  of  pressure. 
From  the  moment  when,  by  means  of  the  enlargement  of  the 
pulmonary  or  thoracic  cone  (we  shall,  in  future,  regard  these 
two  words  as  synonymous),  the  gases  in  the  pulmonary 
reservoir  are  rarefied,  a  blast  of  air  rushes  in  from  the  ex- 
terior, as  the  lung  is  in  free  communication  with  the  air,  and 
this  produces  a  current  from  without  inwards.  We  have 
already  observed  that  the  velocity  of  this  current  differs,  in 
different  zones  of  the  respiratory  reservoir,  owing  to  the  form 
of  the  pulmonary  cone  (see  p.  287). 

B.  Expiration. 

All  this  is,  however,  only  a  part  of  the  act  of  respiration : 
the  introduction  of  air,  or  inspiration,  is  quickly  followed  by 
expiration  or  the  expulsion  of  air  by  a  current  flowing  in  a 
contrary  direction. 

This  latter  movement  takes  place  by  means  of  a  mechanism 
which  differs  entirely  from  that  already  described,  and,  in  the 
normal  condition,  does  not  require  the  intervention  of  any 
extra-muscular  effort.  In  order  to  form  a  clear  idea  of  it, 
we  must  remember  the  exact  structure  of  the  pulmonary 
parenchyma,  and  the  properties  of  its  tissue.  The  envelope 
of  the  alveoli  is  formed  of  elastic  tissue;  it  may,  perhaps, 
contain  some  muscular  tissue ;  but,  if  this  be  so,  the  latter 
very  seldom  gives  rise  to  any  phenomena  of  contraction.^ 
On  this  point  experimenters  are  not  agreed.  Williams  made 
the  experiment  of  passing  an  electric  current  through  the 
lung  of  a  dog,  the  bronchus  being  connected  with  a  mano- 
metric  apparatus;  and  observing  the  variations  which  took 
place  in  the  column  of  mercury  under  the  influence  of  the 
current  he  found  that  there  was  contraction  of  the  smooth 
muscular  fibres,  either  of  the  lung  properly  so  called 
(alveoli),  or  of  the  bronclii.  We  have  repeated  this  experi- 
ment several  times  without  success,  but,  in  spite  of  our  failure,^ 

^  The  name  of  muscles  of  Reisseisen  is  often  applied  to  these 
muscular  fibres,  they  having  been  first  described  by  this  author. 
(Reisseisen,  "  De  Fabrica  Pulmonuiu."     Strasbourg,  1822.) 

^  Paul  Bert  (Legons  sur  la  Physiologic  Comparee  de  la  Respira- 
tion Prof essees  au  Museum  d'llistoire  Naturelle."  Paris,  1870), 
having  made  a  number  of  experiments  on  the  contractility  of 


I 


MECHANICAL  PHENOMENA   OF  RESPIRATION,      297 

we  are  induced  to  believe  that  contraction  of  the  pulmonary 
muscles  takes  place  in  man  in  certain  morbid  conditions,  as 
in  some  forms  of  asthma  or  of  pulmonary  spasms,  which 
appear  to  be  caused,  either  by  paralysis  or  spasms  of  these 
muscles  (the  alveoli  and  the  small  bronchi).  The  contraction 
of  these  muscular  elements  seems,  however,  to  be  of  no  great 
importance  to  the  normal  mechanism  of  respiration.  We 
would  not  be  understood  to  say  that  the  muscular  tissue  is 
of  no  service.  It  must  not  be  forgotten  that  the  elasticity  of 
the  muscle  forms  as  important  a  property  of  this  tissue  as  its 
contractility,  and  is  as  useful  to  the  economy;  we  have 
already  seen,  for  instance,  that  the  elasticity  of  the  inter- 
costal muscles  is  of  more  service  than  their  contraction.  The 
muscular  tissue  which  enters  into  the  construction  of  the 
lungs,  as  it  appears  to  us,  forms  an  elastic  element,  resem- 
bling, physiologically,  the  elastic  tissue,  properly  so  called. 
We  need  not  pursue  the  subject  farther  here,  having  already 
enlarged  upon  it,  in  reference  to  the  structure  of  the  arteries.' 
If  the  lung  is  an  eminently  clastic  tissue,  it  must,  like  the 
arteries,  have  a  natural  form  to  which  it  has  a  constant  ten- 
dency to  return.     We  shall  see  that  this  is  the  case,  and  also 

the  pulmonary  tissue,  deduced  from  them  the  following  conclu- 
sions :  the  pulmonary  tissue  is  contractile  in  mammals  and  in  rep- 
tiles. This  may  be  witnessed  by  means  of  galvanization  with  an 
induced  current,  after  having  fastened  the  trachea,  and  applied 
at  the  opposite  extremity  of  the  lungs  two  large  metallic  plates 
to  serve  as  conductors.  The  manometric  elevation  which  then 
takes  place  is  not  due  to  contraction  of  the  oesophagus  (as  was 
supposed  by  Rugenburg),  for  it  is  seen  even  when  the  lungs  have 
been  extracted  from  tlie  thorax,  and  when  the  heart  and  the 
oesophagus  are  reraoved.  These  contractions  are,  however,  de- 
pendent on  the  pneumo-gastric  nerve.  It  is  very  evident,  on  the 
other  hand,  that  this  contractility  is  of  no  great  physiological 
importance;  if  these  muscles  came  into  play  at  every  respiratory 
movement,  they  would  contract  more  than  twenty  thousand  times  in 
twenty-four  hours,  a  velocity  wliich  would  entirely  contradict  what 
is  positively  known  as  to  the  general  physiology  of  the  smooth 
fibre.  It  is  also  plain  that  the  contraction  of  the"  lung  is  far  too 
slight  to  be  of  any  service,  in  expiration  particularly.  It  may, 
perhaps,  govern  some  kind  of  peristaltic  movement  of  the  bronchi, 
by  means  of  which  the  air  is  mixed  together  (Paul  Bert).  Finally, 
it  is  by  no  means  an  essential  feature  of  the  pulmonary  parenchyma 
and  of  the  respiratory  functions,  for  section  of  the  nerves,  which 
entirely  does  away  with  it  (section  of  the  pneumo-gastric) ,  causes 
no  derangement  in  the  lung  in  this  respect  (P.  Bert). 
*  See  p.  152,  and  the  note  on  p.  154. 


298  PULMONARY  MUCOUS  TISSUE. 

that,  as  with  the  arteries,  this  form  is  never  completely 
attained  during  life.  If  the  thoracic  cage  of  a  dead  animal 
be  opened,  the  lung  is  seen  in  the  form  of  a  spongy  mass, 
lying  firmly  retracted  towards  the  vertebral  column ; 
this  is  not,  however,  the  natural  form  of  the  lung:  the 
muscular  tissue  in  a  corpse  has  lost  its  elasticity,  and  the 
elastic  tissue  alone  remains  in  a  physiological  state.  If,  ngain, 
we  open  the  thoracic  cage  of  a  living  rabbit,  we  find  that  the 
lung  immediately  retracts  towards  the  vertebral  column,  in  a 
much  more  remarkable  degree  than  in  the  dead  body ;  it  is 
reduced  to  a  small  substance  containing  little  or  no  air  or 
blood,  a  comi)act  parenchyma,  hepatized,  we  might  say. 
Should  an  abundant  efi*usion,  filling  one  of  the  pleural 
cavities,  oblige  the  corresponding  lung  to  retract  on  itself,  we 
shall  find  that  it  retracts  as  in  the  foregoing  experiment.  In 
the  case  of  the  lung  of  a  foRtus  which  has  not  breathed,  strong 
points  of  resemblance  to  those  here  mentioned  may  be 
observed. 

The  natural  form  of  the  lung  is  thus  that  of  a  sponge,  a 
bladder  with  numerous  partitions,  firmly  retracted  against 
the  vertebral  column ;  but,  from  the  first  inspiration  of  the 
foetus,  at  birth,  this  form  is  prevented ;  the  thorax  dilates, 
and,  by  means  of  the  pleural  cavity,  forces  the  lung,  as  we 
have  already  seen,  to  develop  in  a  cavity  represented  in  the 
diagram  as  a  cone.  From  that  moment,  on  account  of  the 
rigidity  of  the  ribB,  the  lung  can  never  (unless  in  the  case  of 
perforation  or  efiusion  of  the  pleura)  attain  its  natural  form, 
although  it  is  always  approaching  it,  exactly  as  we  saw  in  the 
case  of  the  arteries. 

Inspiration,  as  we  have  studied  it,  may  be  considered  as  a 
fresh  violence  done  to  the  lung,  opposing  tg  a  greater  degree 
its  natural  fomi.^ 

From  this  point  of  view  it  is  easy  to  comprehend  the 
m.echanism  of  expiration:  as  soon  as  contraction  of  the 
inspiratory  muscles  ceases,  the  pulmonary  elasticity  which 
till  then  has  been  opposed,  re-asserts  itself;  the  lung  retracts 
on  itself,  drawing  with  it,  on  account  of  the  pleural  vacuum, 
the  wall  of  the  thorax.  It  thus  appears  that,  contrary  to 
what  takes  place  in  inspiration,  the  lung  is  active,  and  the 
wall  of  the  thorax  passive ;  but,  in  reality,  both  these  organs 
are  passive.     The  diaphragm  will  act  in  the  same  way ;  if 

*  See  L.  Oger,  '*  Considferations  Physiologiques  sur  la  Forme 
Natiirelle  de  Certains  Organes.  Th^se  de  Strasbourg,  1870,  No.  283. 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      299 


tlie  abdomen  be  opened  and  emptied,  and  the  lower  surface  of 
the  diaphragm  examined,  it  will  be  found  to  have  ascended 
automatically,  as  it  were:  this  is  because  the  lung  has  a 
tendency  to  ascend  quite  high,  and  draws  the  diaphragm 
forcibly  with  it,  by  means  of  the  pleural  vacuum,  which 
obliges  the  diaphragm  to  follow  the  lung  as  we  saw  that  the 
lung  followed  the  diaphragm.  Thus,  in  a  corpse,  the 
diaphragm  is  found  greatly  arched  at  the  top,  and 
very  tense.  Anatomists  know  well  how  favorable  this 
circumstance  is  to  the  dissection  of  this  muscle,  but  they  also 
know  that  the  slightest  stroke  of  the  scalpel,  by  which  it  is 
divided  and  the  air  allowed  to  enter  between  the  two  folds 
of  the  pleura,  immediately  causes  the  muscle  to  descend, 
when  it  becomes  flabby,  loose,  and  no  longer  capable  of  being 
handsomely  dissected. 

In  the  normal  condition,  therefore,  the  mechanism  of 
inspiration  and  expiration  is  entirely  different ;  the  former  is 
actioe,  and  is  produced  by  muscular  contraction ;  the  latter  is 
passive,  and  is  dependent  on  phenomena  of  elasticity  on  the 
part  of  those  organs  which  have  been  opposed  by  inspiration ; 
for  it  is  not  the  elasticity  of  the  lung  alone  which  produces 
this  reaction,  that  of  the  walls  of  the  thoracic  cage,  which 
have  been  equally  opposed,  must  also  be  taken  into  account; 
the  costal  cartilages,  for  instance,  which  during  inspiration 
are  twisted  around  their  axis  m  a  rather  remarkable  manner. 
Finally,  the  viscera  and  the  walls  of  the  abdomen,  having 
been  displaced  during  inspiration,  return  to  their  original 
position,  while  the  stomach  and  intestine,  which  contain  elas- 
tic gases,  by  this  means  force  the  diaphragm  upwards. 

Expiration  may,  however,  be  active  in  certain  cases.  As 
we  have  seen  that  there  is  a  natural,  and  a  forced,  inspiration, 
so  we  find  that  there  is  a  natural,  and  a,  forced,  exjnration; 
in  the  latter  only  do  the  muscles  come  into  play,  those, 
namely,  of  the  abdomen,  the  serrati  postici,  and,  in  general, 
all  those  by  which  the  ribs  can  be  depressed.  This  active 
expiration  takes  place  especially  in  coughing :  the  walls  of 
the  thorax  then  no  longer  simply  follow  the  lung  as  it  draws 
back,  but  compress  it,  thus  increasing  the  rapidity  and  energy 
of  the  expiratory  current  of  air. 

We  cannot  lay  too  much  stress  upon  that  special  function 
of  the  pleural  cavity  by  which,  while  it  permits  the  lungs 
to  move  along  the  inner  surface  of  the  thoracic  wall,  binds 
these  two  surfaces  together,  in  such  a  manner  that  if  the 
thorax  expands,  the  lung  expands  also ;  and  if  the  latter  con- 


300  PULMONARY  MUCOUS  TISSUE. 

tracts,  the  former  contracts  likewise.  The  pleural  folds 
inside  these  two  organs  act  by  means  of  adhesion  by  the 
vacuum,  in  short,  producing  a  sort  of  suction,  resembling  that 
of  cupping-glasses.  It  therefore  appears  surprising  that  what 
takes  place  in  a  cupping-glass,  and  what  physical  laws  would 
seem  to  render  necessary,  does  not  take  place  here,  that  is, 
an  extravasation  of  blood  or  of  serum,  or  permanent  effusion. 
In  ^tVLdymg  the  general  physiology  o^lhQ  epitheliums  (p.  193), 
however,  we  stated  that  this  globular  lining  had  the  power 
to  prevent  such  exudations ;  and  we  find,  in  this  case,  an 
epithelium  to  which  this  function  is  assigned.  Pathological 
observations  confirm  this  view  of  the  matter:  it  has  been 
observed  that  nearly  all  diseases  of  the  pleura,  in  which  effu- 
sion appears,  are  caused  by  more  or  less  entire  destruction  of 
the  epithelium,  or  by  a  state  of  degeneration  which  interferes 
with  the  exercise  of  its  natural  function. 

C.  Function  of  the  air-passages  in  respiration. 

The  air,  being  drawn,  by  the  respiratory  movements,  into 
the  lung,  and  then  driven  out  of  it,  passes  through  the  narrow 
portion  of  our  pulmonary  cone ;  that  is  to  say,  the  nostrils, 
the  nasal  chambers,  the  pharynx,  and  the  trachea  with  the 
larynx.  All  these  tubes  exhibit  mechanical  phenomena, 
accessory  to  those  which  we  have  just  been  studying  in  the 
lung. 

The  nostrils  dilate  actively,  but  only  in  deep  inspirations, 
and  when  there  is  any  sensation  of  dyspnoea;  the  nasal 
chambers  exhibit  no  special  mechanical  phenomena ;  but  we 
know  that  they  perform  an  important  ofiice,  as  being  the 
place  where  the  inhaled  air  is  prepared,  by  being  charged 
with  heat  and  steam. 

On  a  level  with  the  pharynx  the  air-tube  crosses  the  ali- 
mentary canal;  we  saw,  in  studying  the  latter,  how  the 
upper  and  lower  orifices  are  obliterated  as  the  food  passes 
(p.  225). 

In  some  animals  the  communication  between  the  air-tube 
and  the  alimentary  canal  are  permanently  closed:  in  the 
cetaceans  the  trachea  communicates  directly  with  the  nasal 
chambers,  through  which  alone  the  animal  can  breathe.  In 
the  case  of  the  pachydermata,  the  velum  of  the  palate  forms 
at  the  larynx  a  half-ring;  and  the  respiration  is,  consequently, 
exclusively  nasal.  The  horse,  too,  breathes  only  through  the 
nose,  on  account  of  the  disposition  of  the  velum  of  the  palate 
and  of  the  epiglotis,  the  latter  reaching  to  the  posterior 


r 


MECHANICAL  PHENOMENA  OF  RESPIRATION.      301 

orifice  of  the  nasal  chambers.  Consequently,  when  the  facial 
nerve  of  a  horse,  which  innervates  the  muscles  of  the  nos- 
tril, is  cut,  the  nostril  becomes  inert  and  collapsed,  and,  as  in- 
spiration or  expiration  takes  place,  acts  like  a  valve ;  so  that, 
even  if  the  animal  opens  the  mouth  wide,  he  is  asphyxiated, 
in  spite  of  his  efforts  to  breathe.  This  effect  is  peculiar  to 
the  horse,  not  appearing  in  the  dog  or  any  other  animal 
which  breathes  through  the  mouth  (CI.  Bernard).  Finally, 
in  the  human  fcetus,  as  well  as  in  the  foetus  of  the  dog,  it  is 
observed  that  the  larynx  extends  a  little  higher  than  in  the 
adult,  exhibiting,  up  to  a  certain  point,  the  same  disposition 
as  that  which  we  have  just  described  in  the  lower  mam- 
mals. 

The  larynx,  the  trachea  and  its  divisions,  and  the  bronchi, 
form  a  ramified  tube,  which,  like  all  the  constituent  parts  of 
the  respiratory  system,  is  distinguished  by  its  elastic  elements. 
These  are,  first,  its  cartilaginous  rings,  which  are  incom- 
plete behind ;  the  space  left  open,  however,  at  the  back  ot 
these  rings,  is  filled  by  longitudinal  bands  of  elastic  tissue, 
interlaced  and  anastomosed  under  the  mucous  coat.  Deeper 
down,  the  loose  ends  of  each  ring  are  joined  together  by 
smooth  muscular  fibres;  which  continue  as  far  as  the  last 
bronchial  ramifications,  so  that  the  last  cartilaginous  nuclei, 
the  remains  of  the  tracheal  rings,  have  already  disappeared 
while  the  muscular  fibres  are  still  found,  in  greater  numbers 
even,  and  more  uniformly  arranged,  all  around  the  smaller  air 
tubes  (see  p.  281) ;  these  fibres  (muscles  of  Reisseisen)  do 
not  contract  at  will.  We  may  repeat,  in  regard  to  them, 
what  we  have  said  of  the  muscular  fibres  of  the  alveolar  wall 
about  which  some  doubt  exists;  for  there  may  be  other 
muscular  elements  in  the  lungs  than  in  the  small  bronchi  and 
the  small  vessels.  It  is  difficult,  if  not  impossible,  to  prove 
that  these  fibres  contract  in  order  to  take  a  share  in  physio- 
logical actions.  Their  participation  ^  in  pathological  phenom- 
ena is  also  doubtful,  as,  for  instance,  they  do  not  contract 
with  sufficient  force  to  assist  in  coughing ;  the  possibility  of 
their  intervention  in  asthma  and  bronchial  spasms  we  have 
already  noticed.  At  all  events,  what  we  must  recognize  in 
this  element,  as  in  the  preceding,  is  an  eminently  elastic 
tissue,  whose  chief  use  pertains  to  this  property.  Thus  the 
tracheal  and  bronchial  cartilages  resist  the  great  changes  of 
shape,  and  restore  the  tube  to  its  original  form,  when  this  has 

»  See  note  2,  p.  29G. 


302  PULMONARY  MUCOUS  TISSUE. 

been  violated ;  being  aided  in  this  action  by  the  elastic  and 
muscular  tissues. 

The  action  of  the  muscles  of  the  neck  gives  to  the 
trachea  an  ascending  and  descending  motion,  corresponding 
with  the  respiratory  movements.  During  inspiration  the 
trachea  descends;  its  calibre  increases,  and  the  current  of  air 
passes  through  easily,  without  friction.  During  expiration^ 
it  rises^  lengthens,  and  thus  becomes  narrower ;  the  channel 
through  which  the  air  passes  out,  being  narrower  than  that 
through  which  it  entered,  causes  the  air  to  circulate  more 
rapidly,  and  increases  friction  against  the  sides. 

The  larynx  has  also  a  large  share  in  producing  the  differ- 
ence between  the  current  of  air  which  is  inhaled  and  that 
which  is  exhaled.  When  we  study  this  organ  as  a  vocal 
apparatus,  we  shall  find  that  it  is  composed  chiefly  of  an 
antero-posterior  aperture  (glottis),  capable  of  enlarging  and 
of  nai-rowing,  enlargi?ig  in  inspiration^  and  narroicing  in  ex- 
piration. The  degree  of  this  narrowing  differs  in  different 
cases :  when  a  person  makes  a  muscular  effort^  as  for  instance 
in  defecation,  the  opening  is  entirely  closed;  the  air  can 
then  no  longer  escape,  and  is  compressed  by  the  thorax, 
which  forms  a  point  of  support  to  the  muscles  which  are  con- 
cerned in  the  effort. 

The  object  of  the  difference  in  the  velocity  of  the  cur- 
rent of  air  when  inhaled  and  exhaled,  is  the  expulsion  of 
foreign  bodies,  or  rather,  of  those  mucosities  which  may  be 
found  in  the  respiratory  tree.  The  column  of  air,  in  inhala- 
tion, passes  too  slowly  and  with  too  little  friction  to  en- 
able it  to  bring  out  the  mucosities  which  adhere  to  the 
wall ;  the  current  of  exhaled  air,  on  the  other  hand,  present- 
ing the  opposite  conditions,  drags  these  small  collections  of 
matter  forcibly  to  the  upper  orifice  of  the  air-vessels. 

In  coughing^  the  expiration  is  more  sudden,  and  the  pre- 
ceding inspiration  slower  than  the  normal  expiration  and 
inspiration ;  the  chief  effect  of  coughing  is  thus  to  throw  off 
the  mucosities  which  obstruct  the  respiratory  or  air  tubes. 

This  continuous  and  unconscious  expulsion  of  the  mucos- 
ities is  also  effected  by  the  movements  of  the  vibratile  cilia 
with  which  the  columnar  epithelium  of  the  entire  bronchial 
and  tracheal  tubes  (except  at  the  level  of  the  vocal  cords) 
are  furnished ;  the  movements  of  these  cilia  are  of  such  a 
character  that  they  carry  to  the  exterior  all  the  little  bodies 
deposited  on  their  surflice,  conveying  them  as  far  as  to  the 
cavity  of  the  larynx  (see  p.  190).     It  is  here  only  that  expul- 


r 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      303 

sion  becomes  voluntary,  for  it  is  only  in  the  larynx  that  the 
foreign  bodies  or  mucosities  are  perceived ;  lower  down,  the 
sensations  produced  by  their  presence  are  very  slight,  and 
give  rise  to  no  reflex  actions.  The  larynx  is  the  starting- 
point  of  the  reflex  or  voluntary  phenomena  which  produce 
expulsion  by  means  of  this  same  mechanism  of  varying  cur- 
rents of  air,  but  only  with  much  greater  energy ;  it  is  here 
that  coughing  is  produced,  and,  higher  up  (in  the  pharynx  and 
the  nasal  chambers),  sneezing;  and  higher  still  (in  the  nos- 
trils), the  action  of  blowing  the  nose  :  all  these  consisting  in 
a  slow  inspiration  through  a  dilated  orifice,  and  a  sudden 
expiration  through  an  orifice,  narrowed,  either  by  the  con- 
traction of  its  own  muscles,  or  by  a  more  or  less  distant 
mechanism. 


III.   Physical  and  Mechanical  Consequences  of  Respira- 
tion. 

A.  Medianical  effects  produced  upon  the  lung. 

We  have  already  studied  the  numbers  representing  the 
varying  conditions  of  the  blood  in  regard  to  the  intra-pulmo- 
nary  air;  we  must  remember  that  the  respiratory  surface, 
whose  area  is  equal  to  200  square  metres,  is  essentially  repre- 
sented by  a  blood  network  of  150  square  metres;  that  this 
network  represents  a  mass  of  2  litres  of  blood ;  that  this 
blood  is  so  constantly  renewed  that  20,000  litres  of  blood 
pass  through  the  lung  in  24  hours  (Fig.  79).  We  have  now 
to  specify  the  results  of  respiration  in  regard  to  the  quantity 
of  air  brought  in  contact  with  the  blood,  and  the  numerical 
statistics  of  the  agencies  by  which  the  air  is  renewed. 

The  pulmonary  cone  represents  a  reservoir,  the  total 
average  capacity  of  which  amounts  to  4  or  '5  litres,  when 
filled  as  full  as  possible ;  that  is,  when  the  deepest  inspiration 
is  made;  on  the  other  hand,  when  the  strongest  possible 
expiration  is  made,  there  still  remains  in  the  lungs  from  1  to 
1  \  litres  of  residual  air,  which  cannot  be  exhaled  in  any  way, 
because  the  lung,  as  we  have  seen,  can  never  quite  attain  its 
natural  form.  The  difference  between  this  second  figure  and 
the  first  represents  the  quantity  of  air  which  may  be  intro- 
duced into  the  lung  and  then  driven  out,  by  means  of  the 
most  energetic  respiratory  movements :  this  is  what  is  called 
the  vital  capacity  (or  pulmonary  capacity^  or,  better  still, 
respiratory  capacity) ;  it  is  equal  to  8^  litres.  This  figure  is 
of  some  importance,  for  it  indicates  the  magnitude  of  the 


304  PULMONARY  MUCOUS  TISSUE. 

physical  conditions  of  the  gaseous  exchanges,  and  thus  forms, 
as  it  were,  a  measure  of  our  life,  since  to  breathe  is  to  live :  a 
large  number  of  instruments  have  been  constructed  for  the 


Kg.  79.— Circulation  throngh  the  lung.* 

purpose  of  estimating  this  amount ;  of  these,  the  best  known  is 
Hutchinson's  spirometer.^    It  consists  simply  of  a  gasometer 

*  Hutchinson,  *'  Medico-chirurg.  Transactions,"  1846.  More 
Tccently,  the  anapnographer  of  Messrs.  Bcrgeon  and  Kastus  (de 
Lyon)  has  been  employed  for  comparative  estimation.  This  instru- 
ment is,  briefly,  Marey's  sphygmograph,  applied  to  currents  of  air 
which  enter  the  chest  or  leave  it  at  each  respiration;  it  consists, 
chiefly,  of  a  spring  applied  to  the  inspiratory  and  the  expiratory 
current.  A  registering  lever,  furnished  with  a  writing  point, 
grows  broader  at  the  opposite  end,  and  to  this  broader  part  a  tube, 
into  which  the  person  breathes,  is  closely  fitted.  This  part,  which 
is  an  extremely  light  and  delicate  plate  of  aluminium,  serves  as  a 
valve,  kept  immovable  and  vertical  by  two  opposite  springs  of  equal 
force,  but  moving  with  each  respiratory  current,  and  drawing  after 
it  the  writing  lever,  which  traces  on  the  paper,  first  by  vertical  and 

*  a,  b,  Right  heart  (venous  blood),  ff,/,  Left  heart  (arterial  blood),  c,  Pul- 
monary artery  and  its  branches  (carrying  the  venous  blood  into  the  lung), 
c.  Pulmonary  veins  (rarely  containing  arterial  blood),  d,  Vascular  network  of 
the  lung.    A,  Aorta.    (Dalton,  "Human  Physiology.") 


r 


MECnANICAL  PHENOMENA   OF  RESPIRATION.      305 

immersed  in  a  water  receiver,  and  to  which  an  india-rubber 
tube  is  attached,  one  end  of  which  is  placed  in  the  mouth  of 
the  person  experimented  upon.  The  movements  in  the  air- 
receiver  are  recorded  by  means  of  a  movable  indicator  and  a 
.graduated  and  fixed  scale.  The  person  first  takes  a  deep 
inspiration,  and  then  breathes  into  the  tube,  and  thus  the 
maximum  volume  of  the  air  inhaled  is  obtahied.  After  ex- 
perimenting in  this  manner  on  about  2000  persons,  Hutch- 
inson lays  it  down  as  a  law  that  the  maximum  volume  of  air 
exhaled  in  the  normal  condition  is  in  regular,  if  not  mathe- 
matical proportion  to  the  stature.  In  an  athletic  native  of 
America,  he  found  that  the  maximum  volume  of  air  exhaled 
was  7  litres  (althougli  the  man  died  of  consumption  a  few 
years  after).  We  give  (Fig.  80)  a  sketch  of  Schnepl's  spi- 
rometer; it  is  only  Hutchinson's  instrument  modified.  The 
air,  exhaled  through  the  tube  A,  is  received  into  the  receiver 
C,  wliich  serves  as  a  gasometer.^ 

The  numbers  given  above  represent  extraordinary  cases; 
in  caliu,  ordinary  respiration  only  one-half  lilre  of  air  is  intro- 
duced at  each  inspiration,  and  given  out  at  each  expiration. 
The  latter  may  be  called  the  figure  of  normal  respiration. 

then  by  horizontal  lines,  the  movements  of  the  valve,  that  is,  the 
impressions  which  it  receives,  as  well  as  the  spring,  from  more  or 
less  intense  or  prolonged  currents  of  air.  The  exquisite  sensibility 
of  this  instrument,  recording  the  slightest  movements  of  the  air, 
such  as  the  bursting  of  a  bubble  in  a  flask,  enables  us  exactly  to 
determine  the  frequency  of  the  respiratory  movements,  the  relative 
length  of  each,  their  intensity,  and,  especially,  their /orm.  (Ber- 
geon  and  Kastus,  "  liecherches  sur  la  Physiologie  Medicale  de  la 
Jlespiration,  a  I'Aide  d'un  nouvel  Instrument,  TAnapnographe." 
Paris,  18U9.)  These  writers  have  here  made  a  collection  of  dia- 
grams of  remarkable  accuracy,  exhibiting  special  features,  accord- 
ing to  the  age  of  the  subject,  the  exaggerated  exercise  or  morbid 
condition  of  the  lungs,  etc. 

The  spirometer,  evidently,  might  be  employed  to  ascertain  the 
diminution  in  the  pulmonary  capacity  at  the  beginning  of  phthisis, 
when  physical  signs  (auscultation)  leave  the  physician  in  doubt;  but, 
for  this  purpose,  it  must  have  been  previously  measured  in  health. 
Any  disease,  such  as  emphysema,  pleurisy,  etc.,  which  diminishes 
the  space  occupied  by  the  air,  or  diminishes  the  quantity  of  air  in 
circulation,  produces  the  same  effect  as  phthisis.  Spirometry, 
therefore,  cannot  be  said  to  be  of  any  great  use  in  medical  prac- 
tice. 

'  Schnepf,  '♦  Capacity  Vitale  du  Poumon,  ses  Rapports  Physi- 
ologiques  et  Pathologiques  avec  les  Maladies  de  la  Poitrine.'* 
1858. 

20 


806 


PULMONARY  MUCOUS  TISSUE. 


In  order  to  ascertain  exactly  the  capacity  of  the  lungs,  and 
the  quantity  of  air  introduced  into  them,  the  different  por- 

tions  of  which  this  air  is 
successively  composed  must 
be  demonstrated  :  that  por- 
tion of  the  air  which  cannot 
be  driven  out  of  the  lungs 
by  the  most  forcible  expira- 
tion is  called  residual  air 
(a) ;  the  air  which  may  still 
be  expelled  after  an  ordinary 
expiration  (though  showing 
the  difierence  between  a 
moderate  and  a  forced  ex- 
piration) is  called  air  in 
reserve  (b) ;  the  air  which 
we  inhale  and  exhale  at  each 
ordinary  respiration  is  called 
the  respiratory  air  (c) ;  fin- 
ally,that  quantity  of  air  which 
we  can  inhale  by  means  of  a 
forcible  inspiration  (or  the 
difference  between  normal 
and  forced  ins])iration)  is 
called  complemetUari/  air 
(Hermann). 

I'hese  names  being  accept- 
ed, nothing  is  easier  than  to 
estimate  the  last  quantity  (d) 
experiment.illy:  the  numeri- 
cal value  of  the  complement- 
ary air  varies  essentially  with 
individuals,  the  diversity  a[»- 
pearing  to  depend  less  on 
the  size  of  the  individual, 
than  on  the  confirmation  of 


Fig.  80.  — Schnepf'8  Spirometer.* 


the  chest.  The  quantity  increases  with  the  increase  of  the 
transverse  diameter  of  the  cavity  of  the  thorax.  The  three 
diameters  of  the  lung,  or,  what  is  the  same  thing,  of  the 


*  V,  Brass  cylinder.  TT,  Respiratory  tube.  A,  Mouth  of  (lie  respiratory 
tube.  C,  Receiver  or  gasometer.  P,  Balance-weight.  S,  Chain.  R,  Pulley. 
L,  Scale.  M,  Upright  bar.  G,  Case,  supporting  the  scale.  N,  Surface  of  the 
fluid  contained  in  the  reservoir.  E,  Bottom  of  the  gasometer.  O,  Open  mouth 
of  the  gasometer. 


MECHANICAL  PUENOMENA   OF  RESPIRATION.      307 

thoracic  cavity,  differ  greatly  in  importance,  and,  in  this 
respect,  the  transverse  diameter  far  surpasses  the  two  others. 
(Sappey.) 

The  quantity  c,  or  air  of  respiration  (ordinary),  may  also 
be  easily  estimated :  this  is  done  by  collecting  the  gas  ex- 
pelled from  the  lungs  by  a  certain  number  of  expirations, 
measuring  it,  and  dividing  the  quantity  thus  obtained  by 
the  number  of  expirations.  It  is,  however,  difficult,  during 
the  experiment,  not  to  change  the  number  and  extent  of  the 
respiratory  movements.  Grehant,  nevertheless,  succeeded  in 
obtaining  perfect  precision,  by  special  controlling  methods, 
founded  on  analysis  of  the  air  exhaled,  at  the  beginning  and 
at  the  end  of  the  experiment;^  he  has  thus  estimated  the 
quantity  c  at  -^^^q  of  a  litre,  which  is  nearly  the  saijie  as  the 
standard  \  litre  (Dalton,  Valentin,  Berard). 

The  other  two  quantities,  air  of  reserve  (J),  and  residual 
air  (a),  are  much  more  difficult  to  determine:  they  can  be 
measured  only  in  a  roundabout  way.  The  sum  of  these  two 
quantities  (a  +  b)  is  first  measured,  and  then  that  of  one  of 
them  (a)  ;  the  value  of  the  third  unknown  (b)  is  obtained 
by  subtraction. 

Grehant  has  estimated  the  sum  a  -\- b  with  the  greatest 
accuracy :  his  method  is  based  on  the  same  principle  which 
we  have  already  seen  employed  in  estimating  the  quantity 
of  blood  contained  in  the  circulating  reservoir  (see  p.  111). 
In  order  to  measure  the  blood  contained  in  the  vessels,  we 
ascertain  the  degree  of  dilution  which  it  undergoes  by  means 
of  the  injection  of  a  certain  quantity  of  water;  in  order  to 
measure  the  volume  of  air  remaining  in  the  lungs  after  an 
ordinary  expiration  {a  -\-  b),  the  gases  which  are  then  con- 
tained in  the  respiratory  tree  or  system  are  carefully  mixed 
with  a  known  quantity  of  hydrogen,  and  the  analysis  of  the 
mixture  is  then  made  by  means  of  the  eudiometer.  Thus, 
after  an  ordinary  expiration  in  the  air,  the  person  making  the 
experiment  begins  to  breathe  into  a  receiver,  containing  500 
cubic  centimetres  of  pure  hydrogen;  after  the  fifth  respiratory 
movement,  the  mixture  is  })erfected,  that  is,  it  is  exactly  the 
same  in  the  receiver  and  in  the  lung  (see  p.  288).  It  is  only 
requisite  tlien  to  analyze  the  gases  in  the  receiver  to  obtain, 
by  a  simple  calculation,  the  volume  of  air  contained  in  the 
lung  at  the  beginning  of  the  experiment,  that  is,  after  ordi- 

'  See  **  Journal  de  I'Anatomie,"  etc.,  de  Charles  Robiu,  186i, 
p.  542. 


808  PULMONARY  MUCOUS  TISSUE. 

nary  respiiation,  or,  in  other  words,  calculate  the  volume  a  -}- 
b.  For  persons  whose  ages  are  between  17  and  35  years, 
Grdhant  obtained,  in  this  manner,  quantities  varying  between 
2-1^^  litres,  and  3^o^  litres.  (Grehant  calls  this  quantity 
the  pulmonary  capacity:  this  is  not  the  meaning  usually 
attached  to  this  expression :  if  we  refer  to  what  was  said 
above,  we  shall  find  that  the  •pulmonary  or  vital  capacity 
represents  the  sum  h  -\'  c  -\-  d ;  while  that  settled  by  Gre- 
hant represents  the  sum  a  -\-h. 

The  quantity  a  remains  to  be  determined,  and  this,  too, 
Grehant  enables  us  to  do.  "  In  order  to  decide  this,  I  intro- 
duce a  half-litre  of  air  into  a  receiver  (with  a  stop-cock)  ; 
after  an  expiration  made  in  the  air,  I  inhale  this  gas,  and 
then  make  as  long  an  expiration  as  possible  into  the  receiver : 
I  then  measure  the  volume  of  the  exhaled  gases ;  I  find  that 
is  1.8  litre.  The  pulmonary  capacity  (a  -f-  6,  say  2.34  litres) 
is  increased  by  the  inspiration  of  J  litre,  and  diminished  by 
1.8  litre:  what  remains  in  the  lungs  is,  therefore,  2.34  litres 
-f-  0.5  —  1.8  litres  =  1.04  litres."  Thus  the  quantity  a  (re- 
sidual air),  which  includes,  it  must  be  remembered,  the 
volume  of  the  buccal  cavity,  is  about  equal  to  one  litre} 

The  same  experiment  gives  us  the  value  of  J,  or  the  air  in 
reserve.  We  have  thus  all  the  data  necessary  to  solve  the 
physiological  problems  relating  to  the  quantities  a,  ^,  c,  d. 

One  of  the  most  important  of  these  problems  is  that  of  the 
ventilation  of  the  lung^  which  Grehant  was  the  first  to  solve. 
The  quantity  of  fresh  air,  which,  after  each  movement  of  ven- 
tilation, remains  in  the  unit  of  volume  in  the  ventilated  space, 
is  called  the  coefficient  of  ventilation  :  the  lung  is  a  space  of 
this  kind,  and  the  respiratory  movement  really  forms  a  ven- 
tilating movement.  The  coeflicient  of  ventilation  is,  there- 
fore, the  quotient  obtained  by  dividing  the  quantity  (x)  of 
pure  air  remaining  in  the  lung  after  a  normal  expiration  and 
inspiration,  by  the  known  volume  of  the  lung  after  such  ex- 
piration {a-{'b  =  2.365  1.,  for  instance).  Grehant  discovered, 
by  means  of  the  inspiration  of  hydrogen,  already  mentioned, 
that  the  quantity  x  =  on  an  average  0.328  1.  (that  is  to  say 
that,  when  an  ordinary  inspiration  or  expiration  is  made,  each 

*  We  follow  the  example  of  most  physiologists  in  calling  this 
quantity  "residual  air,"  but  we  must  forewarn  the  reader  that 
Grehant  gives  it  the  name  of  "  air  in  reserve,"  a  name  which  more 
naturally  applies  to  the  quantity  b.  (See  "  llevue  des  Cours  Scien- 
tifiques."     Aout,  1871.) 


r 


MECHANICAL  PHENOMENA  OF  RESPIRATION.      309 

being  equal  to  a  half-litre,  about  one-third  of  the  air  inhaled 
is  given  back  to  the  atmosphere,  while  two-thirds  of  pure  air 
enter  the  lung,  and  renew  its  contents  by  mixing  with 
them).  The  coefficient  of  pidmonary  ventilation  is,  there- 
fore, -^^^  =  0.145 ;  or  a  little  more  than  ^.  It  varies, 
however,  with  the  volume  of  the  lungs,  and  with  the  volume 
of  inspiration.  Grehant  has  obtained  extremely  interesting 
results  from  this  point  of  view.  Thus  he  found  that  an  in- 
spiration of  J  litre  renews  the  air  in  the  lungs  better  than  two 
inspirations  of  300  cubic  centimetres,  forming,  together.^  600 
cubic  centimetres.  "  This  is  the  reason  that  in  certain  affec- 
tions of  the  chest,  in  which  patients  inhale  frequently,  but 
not  deeply,  the  air  is  not  renewed  so  perfectly  as  in  the 
normal  state ;  40  inspirations,  of  300  cubic  centimetres  each, 
not  producing  such  entire  renovation  of  the  air  as  20  inspira- 
tions of  500  cubic  centimetres." 

Such  is  the  estimate  of  the  quantities  of  air  introduced 
into  the  lung:  the  frequency  with  which  the  movements 
producing  this  renovation  of  the  air  are  performed  is  easily 
ascertained ;  we  breathe  13  or  14  times  in  a  minute,  thus 
making  the  number  of  inspirations  20,000  in  24  hours ;  as 
each  inspiration  introduces  ^  litre  of  air  into  the  lungs,  we 
breathe  altogether  10,000  litres  of  air  in  a  day.  The  quantity 
of  blood  brought  into  contact  with  this  air  has  a  very  simple 
numerical  relation  to  it,  being  20,000  litres,  or  rather  10,000 
litres  of  globules  (1  litre  of  blood  =  ^  litre  of  globules,  or 
cruor  -j-  ^  litre  of  liquor). 

The  differences  of  pressure,  caused  by  the  mechanical 
working  of  the  thorax,  and  which  are  intended  to  produce 
the  movements  of  the  air,  are  also  very  slight  in  the  normal 
condition  :  if,  for  instance,  we  represent  the  exterior  pressure 
(atmospheric  pressure),  in  the  state  of  repose,  by  100,  the 
intra-pulmonary  pressure  will  be  ICO  also.  The  dilatation 
produced  by  inspiration,  however,  causes  the  interior  pres- 
sure to  descend  to  99  5,  and  thus  the  interior  air  penetrates 
the  lung  (^  a  litre,  as  we  have  said).  When  the  normal 
expiration  occurs,  the  intra-pulmonary  jn'essure  rises  to 
100.5,  and  a  quantity  of  gas  equal  to  that  which  has  entered 
the  lungs,  is  thrown  off. 

In  forcible  respiratory  movements,  however,  these  figures 
are  mufch  larger:  thus  inspiration  may  reduce  the  interior 
pressure  to  75,  while  expiration  may  increase  it  to  130  or 
135 ;  in  other  words,  in  a  very  forcible  inspiration,  the  interior 
pressure  differs  from  the  exterior  by  4,  and  in  forcible  expira- 


BIO  PULMONARY  MUCOUS  TISSUE. 

tion,  by  ^  of  that  of  the  atmosphere.  We  see  that  the  differ- 
ence is  greater  in  expiration  than  in  inspiration,  in  the  case 
of  an  energetic  movement :  as  we  know  that  more  mechani- 
cal effect  is  produced,  for  instance,  by  blowing  through  a 
tube,  than  by  inhaling  through  it.  The  reason  of  this  differ- 
ence is  evident,  if  we  remember  that  the  contraction  of  the 
inspiratory  muscles  is  impeded  by  the  elasticity  of  a  number 
of  organs  which  are  disturbed  by  such  contraction  (the  lungs, 
costal  cartilages,  abdominal  viscera,  &a)  ;  while  the  expiratory 
muscles,  which  are  at  least  as  powerful  as  their  antagonists, 
have  only  to  add  their  force  to  that  of  these  elastic  parts 
acting  in  the  same  direction.  This  power  of  forced  expira- 
tion, joined  to  the  mechanical  conditions  produced  by  the 
contraction  of  the  trachea  and  the  glottis,  serve  to  promote 
the  expulsion  of  foreign  bodies,  or  mucosities  (coughing). 

We  repeat  that  this  difference,  on  the  side  of  expiration, 
exists  only  in  the  case  of  forcible  respiration :  in  the  normal 
condition  expiration  is  only  a  reaction  of  the  elasticity  of  the 
organs  overcome  by  inspiration ;  and  thus  one  has  nearly  as 
much  power  as  the  other.  But  they  are  not  both  of  the  same 
type,  the  same  form,  or  the  same  duration;  that  is  to  say, 
inspiration,  produced  by  muscular  contraction,  takes  place  in 
a  manner  nearly  uniform,  and  may  be  represented  by  a  regu- 
larly ascending  line ;  while  expiration,  on  account  of  the  way 
in  which  it  is  produced,  follows,  in  its  form,  the  same  law  as 
the  elastic  bodies :  for  instance,  if  we  compress  a  gas  in  a 


Fig.  81.  — Normal  kymograpMc  tracings  of  tlie  respiratory  movements 
in  man  (Marey).* 

syringe,  by  means  of  a  piston,  we  shall  find  that  the  moment 
we  cease  to  press  the  latter,  it  rises  .up,  suddenly  at  first,  but 

*  The  descending  line  is  that  of  inspiration,  the  ascending  that  of  expira- 
tion, the  pen  moving  from  left  to  right. 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      311 

afterwards  the  ascending  reaction  continues  more  slowly;  the 
same  is  true  with  expiration,  which,  sudden  at  first,  con- 
tinues with  a  slow  movement,  lasting  a  considerable  time 
(Fig.  82,  3)  :  it  may  be  represented  in  a  diagram  by  a  line 
descending  suddenly,  and  almost  vertically,  and  then  by  a 
very  long  and  oblique  descending  line  (Fig.  81  and  82). 
Thus  expiration,  in  short,  occupies  a  longer  time  than  inspira- 
tion ;  a  superficial  examination,  however,  shows  only  the  first 
period  of  expiration,  which  then  appears  extremely  short, 
shorter  even  than  inspiration. 

The  passage  of  the  air  through  the  respiratory  tubes  pro- 
duces certain  kinds  of  friction,  and  causes  the  inspiratory  and 
expiratory  murnmr  {bruit)  :  the  former  sound  lasts  as  long 
as  the  action  producing  it ;  the  latter  is  usually  perceived 
only  during  the  first  part  of  this  action,  the  current  of  air 


Fig.  82.  —  Kymographic  tracings  of  the  respiration  of  a  dog  * 

being  too  slow  and  feeble  in  the  second  part,  to  make  itself 
heard.  We  see  thus  that  auscultation  of  the  normal  respira- 
tion would  give  a  false  idea  as  to  the  relative  duration  of  the 
two  acts  constituting  respiration,  by  representing  inspiration 
as  occupying  a  longer  time  than  expiration ;  what  is  true  in 
regard  to  the  sounds  ])roduced  not  being  true  in  regard  to 
the  causes  which  produce  them. 

Since  the  discovery  of  auscultation  by  Laennec  many  the- 
ories have  been  propounded  which  seek  to  explain  the  sound 
produced  by  normal  respiration,  and  the  changes  which  it 

*  The  double  line  (3)  especialljir  represents  the  difference  between  inspiration 
and  expiration.  The  respiration  is  recorded  at  the  same  moment  in  the  tracliea 
(by  variations  of  manometric  pressui-e)  and  in  the  thorax  (the  registering  drum 
and  lever  being  moved  by  the  dilatations  of  the  chest) :  these  two  tracings  are 
contrasted  for  comparison.  (P.  Bert,  "Le9ons  sur  la  Physiologic  coniparee  de  la 
Respiration.") 


312  PULMONARY  MUCOUS  TISSUE. 

undergoes  m  pathological  cases.  The  respiratory  murmur 
is  evidently  caused  by  friction  against  the  sides  of  the  air- 
vessels,  but  it  is  not  easy  to  decide  exactly  where  this  mur- 
mur is  localized.  It  was  formerly  attributed  to  the  unfolding 
of  the  pulmonary  vesicles,  whence  the  name  of  vesicular 
murmur.  Beau,  however,  maintains  that  its  sent  is  at  the 
opening  of  the  glottis;  many  physiologists  have  adopted  tliis 
opinion,  while  Bergeon  has  recently  (18G9)  combined  the 
two  theories,  slightly  modifying  both,  lie  holds  that  the 
inspiratory  sound  is  produced  in  two  places,  the  glottis  and 
the  lung,  while  the  expiratory  sound  is  produced  in  the 
glottis  only ;  the  former  being  caused  by  the  passage  of  the 
air  through  the  constricted  orifices,  this  passage  being  accom- 
panied by  the  formation  of  fluid,  vibrating  veins  (see  Circu- 
lation^ p.  164) ;  these  veins  are  formed  both  at  the  glottis  and 
at  that  of  the  opening  of  the  small  bronchi  into  the  pul- 
monary alveoli.  The  cause  producing  the  respiratory  sounds 
cannot  be  supposed  to  exist  only  at  the  level  of  tlie  glottis, 
for  the  sound  continues  the  same  in  cases  in  which  the  air  no 
longer  passes  through  the  larynx,  as  after  operations  in 
tracheotomy.  We  may,  therefore,  conclude  that  the  causes 
of  the  respiratory  murmur  are  manifold,  and  the  principal 
one  may  be  said  to  be  (Sabati.er)  the  dull  crepitation  pro- 
duced by  the  detachment  of  the  trabeculae,  or  slightly 
moistened  partitions  of  the  pulmonary  alveoli;  the  vibra- 
tions made  in  the  air  at  the  sharp  edges  formed  by  the  bron- 
chial bifurcations;  the  friction  of  the  air  against  the  bronchial 
coats ;  and,  finally,  the  more  or  less  decided  resonance  of  the 
superior  or  glottic  sounds.^ 

B.  Mechanical  effects  produced  by  respiration  in  the  organs 
adjacent  to  the  lungs. 

The  mechanical  consequences  of  the  inspiratory  and  ex- 
]  iratory  movements  are  not  confined  to  the  air-vessels ;  the 
blood  vessels  and  the  circulation  of  the  blood  are  also  affected 
by  these  movements,  the  greater  part  of  the  circulating 
system  being  contained  in  the  cavity  of  the  thorax. 

We  have  represented  the  circulation  in  a  diagram,  by  the 
figure  of  8,  the  upper  half  representing  the  pulmonary  circu- 
lation, and  the  lower,  the  general  circulation,  the  point  of 

1  See  "  Les  Nouvelles  Recherches,"  de  V.  Cornil;  "  Anatoraie 
Pathologique  et  Auscultation  du  Poumon."  Mouvement  madical, 
Avril  et  mai,  1873. 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      313 

junction  being  occupied  by  the  heart  (see  Fig.  42,  p.  143) ; 
the  cavity  of  the  lungs  contains :  1.  All  that  portion  of  the 
circulation  called  pulmonary,  that  is,  the  upper  circle ;  2.  The 
point  of  junction  of  these  two  circles,  viz.,  the  heart ;  and  3. 
The  lateral  origins  of  the  lower  circle,  or  the  summit  of  the 
arterial  and  of  the  venous  cone.  The  changes  in  intra- 
thorncic  pressure  affect  all  these  three  portions. 

This  influence  is  counteracted,  however,  in  the  case  of  the 
circulation  of  the  thorax^  by  the  fact  that  the  venous  cone  of 
this  circulation  is  subjected  to  the  same  variations,  and 
simultaneously,  as  the  arterial  cone;  and  as  the  differences  of 
intravascular  pressure  which  produce  the  circulation  remain 
the  same,  no  change  in  the  circulation  occurs;  the  circulation 
is  but  slightly  influenced,  except  by  the  more  or  less  com- 
plete expansion  of  the  alveoli,  which  occasions  a  greater  or 
less  permeability  of  the  capillary  vessels,  or,  in  other  words, 
of  the  base  of  the  pulmonary  cone. 

The  influence  of  respiration  is  much  more  sensibly  felt  in 
the  heart :  an  expiration  made  with  force,  as  in  any  great 
exertion,  causes  immense  pressure  upon  the  heart,  and  as  the 
coats  of  this  cavity  are  thin,  and  easily  compressed,  a  deform- 
ation ensues.  Weber  has  made  experiments  to  show  this,  by 
first  making  an  extremely  deep  inspiration,  and  then  very 
forcible  movements  of  expiration,  the  glottis  being  closed, 
and  the  arms  kept  fixed  against  his  sides.  After  the  lapse  of 
a  few  seconds,  a  change  is  observed  in  the  pulse,  which  becomes 
slower,  and,  at  length,  ceases  entirely ;  if  the  ear  is  placed 
over  the  chest,  no  sound  is  heard,  whence  we  may  infer  that 
the  heart  has  ceased  to  beat.  If 'the  experiment  be  continued, 
the  person  loses  consciousness,  and  thus,  in  spite  of  himself, 
returns  to  his  original  state  of  life  and  circulation. 

If,  however,  the  person  remains  passive,  the  stoppage  of  the 
heart  continues,  and  may  end  in  death ;  this  is  probably  the 
case  with  persons  who  are  squeezed  to  death  in  a  turbulent 
crowd,  the  outside  pressure  being  continued  even  after  syn- 
cope has  been  produced.^  In  experiments  or  accidents  of 
this  kind,  the  stoppage  is  not  the  same  in  all  parts  of  the 

^  A  case  has  been  reported  by  the  American  editor  ("  Boston 
Med.  &  Surg.  Journal,"  Dec.  11,  1873,  p.  577),  in  which  a  rup- 
ture of  the  right  auricle  was  caused  by  compression  of  the  thoracic 
walls.  Another  accident  (reported  in  the  "  Gaz.  Ilebd.,"  March 
27,  1871,  p.  199,  by  MM.  IJoubre  and  Charpentier)  of  compression 
of  the  thorax  between  a  wheel  and  tlie  ground,  resulted  also  in  the 
rupture  of  the  right  auricle. 


314  PULMONARY  MUCOUS  TISSUE. 

heart :  it  takes  place  chiefly  in  the  right  auricle.  The  effect 
produced  may  be  shown  by  exposing  the  heart  of  a  frog, 
and  compressing  it  at  the  point  of  the  opening  of  the  vena 
cava,  and  thus  preventing  the  entrance  of  the  blood:  the 
entire  heart  then  ceases  to  beat,  because  the  ventricle,  as  well 
as  the  auricle,  receiving  no  more  blood,  there  is  no  longer  on 
the  inner  surface  of  these  cavities  any  impression  which  may 
s^rve  as  a  point  of  origin  of  the  reflex  action  which  causes  the 
pulsation  of  the  heart.  If  the  man  or  animal,  however,  is  in 
a  state  of  perfect  health,  it  is  not  very  likely  that  this  mechan- 
ism of  compression  w^ill  produce  death.  Indeed,  though  the 
heart  stops,  the  arteries  by  means  of  their  elasticity  drive 
their  contents  into  the  veins,  which  become  turgid,  while  the 
summit  of  the  venous  cone  quickly  pours  into  the  heart  a 
mass  of  blood,  thus  setting  the  heart  in  motion  again.  The 
mechanism  which  we  have  described,  however,  explains  the 
so-called  voluntary  stoppage  of  the  heart,  of  which  some  per- 
sons have  professed  to  be  capable :  the  will  acts  upon  the 
heart,  in  this  case,  only  through  the  medium  of  respiration. 

Respiration  produces  a  similar  eftect  on  the  general  circula- 
tion, the  top  of  the  two  cones  (the  arterial  and  the  venous) 
being  included  in  the  thorax.  We  know  that  at  the  top  of 
the  venous  cone  the  pressure  is  so  slight  that  it  may  be  repre- 
sented by  0  or  y J  ^j ;  at  the  top  of  the  arterial  cone,  on  the 
other  hand,  the  contraction  of  the  ventricle  produces  a  pres- 
sure which  may  be  reckoned  as  -^^'^  (see  p.  143). 

Let  us  su))i)ose  that,  by  means  of  a  strong  expiration,  a 
pressure  of  -^^^j  is  produced  in  the  cavity  of  the  thorax :  the 
pressure  at  the  top  of  the  venous  cone  will  then  be  ^y%  an 
enormous  pressure  for  this  part  of  the  circulating  system,  an 
essential  feature  of  its  working  condition  being  the  absence 
of  all  pressure.  The  consequence  will  be  a  considerable  reflux 
into  the  veins;  this  retlux  into  the  veins  near  the  heart  is 
prevented  by  the  numerous  valves  with  which  they  are  fur- 
nished, and.it  is  only  at  the  top  of  the  cone  that  the  j)ressure 
is  made.  As  the  blood  continues  to  flow,  and  finds  an 
obstruction  to  its  further  progress,  stagnation  follows,  accom- 
panied by  distention  of  the  veins  acljacent  to  the  thorax. 
This  is  chiefly  seen  in  straining,  and  in  those  processes  which 
are  accomi)anied  by  it,  as  parturition,  defecation,  &c.;  the 
signs  of  the  stagnation  of  the  blood  are  injection  of  the  eyes, 
redness  of  the  face,  cessation  of  the  cerebral  circulation,  and, 
finally,  the  suppression  of  the  functions  of  the  brain  (vertigo 
and  even  ai)Oplexy)  :  a  state  of  less  entire  stagnation,  often 


MECHANICAL  PHENOMENA   OF  RESPIRATION.      315 

repeated,  causes  dilatation  of  the  veins,  varices,  vascular 
hypertrophy  of  the  thyroid  gland,  &c. 

This  influence  of  expiration  produces  equally  marked  effects 
in  the  arterial  cone.  At  the  top  of  this  cone,  the  pressure 
produced  by  the  ventricle  is  -,2_5_.  If  we  assume  the  pressure 
in  the  thorax  at  j^jp^^  in  the  arterial  cone  it  will  be  ^*f^ ;  this 
causes  the  arterial  blood  to  flow  much  faster,  there  being  here 
nothing  which  can  counteract  or  delay  the  eflfect  of  this 
increase  of  pressure ;  and  the  fluid  is  forced  into  the  arteries 
by  two  pumps,  the  heart  and  the  thorax.  It  is  true  that  the 
slackening  of  the  flow  of  the  blood  in  the  veins  has  a  ten- 
dency to  counterbalance  its  increased  rapidity  in  the  arteries, 
but,  in  spite  of  this,  immense  pressure  is  produced  on  the 
entire  current  of  the  circulation,  accompanied  by  a  strong 
tendency  to  hemorrhage,  ruptures  of  aneurisms,  varicose 
dilatations,  &c.^ 

Tlie  phenomena  which  follow  a  diminution  of  pressure  in 
the  thorax,  produced  by  a  violent  inspiratory  movement,  are 
entirely  diflerent  from  the  above.  The  pressure  at  the  top  of 
the  venous  cone  then  becomes  less  than  0,  or,  in  fact,  aspira- 
tion of  blood  by  the  veins,  an  increased  acceleration  of  the 
circulation  of  the  venous  blood ;  if  the  blood  does  not  flow 
in  sufiicient  quantity  to  satisfy  this  aspiratory  demand,  the 
coats  of  the  veins  become  relaxed,  and  show  a  tendency  to 
collapse.  In  the  veins  which  are  near  the  thorax,  and  are 
especially  under  the  influence  of  this  aspiration,  the  rela- 
tions between  the  coats  of  the  veins  and  the  aponeuroses 
are  such  that  these  vessels  remain  constantly  o]>en :  the 
aspiration  is  thus  continued  to  veins  more  remote  from  the 
heart.  In  a  surgical  operation,  therefore,  if  one  of  the  veins 
near  the  thorax  be  opened,  the  outer  air,  at  the  moment  of 
inspiration,  may  be  drawn  into  the  interior  of  the  vessel,  an 
occurrence  which  is  generally  followed  by  speedy  death. 

Under  the  influence  of  this  inspiratory  aspiration,  the  aortic 
pressure,  which  is  ^^^^j,  falls  to  y\f(y,  or  -jJ^o^,  causing  a  slackening 
of  the  circulation,  diuiinished  tension  of  the  vessels,  feeble- 
ness of  the  pulse,  &c.  But  while  the  conditions  of  expiration 
were  favorable  to  hemorrhage,  these  resist  it,  and,  in  order  to 
arrest  the  flow  of  blood,  it  is  sometimes  only  necessary  to 
cause  the  patient  to  make  several  deep  inspirations. 

These  results,  at  which  we  have  arrived  by  simple  reason- 

^  See  F.  Guyon,  "  Note  sur  1' Arret  de  la  Circulation  Caroti- 
diemie  pendant  T Effort."     Archives  de  Physiologie,  1866. 


ol6  PULMONARY  MUCOUS  TISSUE. 

injr,  have  been  experimentally  verified  by  Marey,  by  means 
of  the  graphic  metliod.  This  physiologist  has  reached  the 
following  conclusions  in  regard  to  the  effect  produced  on  the 
circulation  by  respiration.  Respiration  affects  the  pulsation 
of  the  heart ;  it  not  only  causes  variation  in  the  line  of  the 
whole  tracing,  but  imparts  to  the  pulsations  produce<l  during 
inspiration  an  amplitude  and  a  form  which  differ  from  those 
observed  during  expiration ;  when  respiration  is  stopped,  the 
pulsation  of  the  heart  slackens  and  diminishes  in  intensity : 
these  modifications  are  explained  by  the  fact  that  the  blood 
passes  less  readily  through  the  lung  when  the  latter  is  not  in 
action.  After  an  effort  (forcible  attempt  at  expiration,  the 
glottis  being  closed)  the  pulsation  of  the  heart  assumes 
special  features.  The  left  ventricle  makes  its  action  intensely 
perceptible,  while  the  blood  in  the  auricle  is  violently  pre- 
cipitated at  the  period  at  which  the  diastole  begins.  If  the 
person  experimenting  breathe  through  a  narrow  tube,  the 
relation  between  the  pulsation  of  the  heart  and  the  respira- 
tory movements  is  changed :  while  the  respiration  becomes 
less  frequent,  the  pulsations  become  more  rapid. 

We  also  find  in  the  pulse  differences  corresponding  to  the 
different  respiratory  types  (thoracic  and  abdominal  types,  see 
p.  295).  The  thoracic  type  exhibits  a  diminution  of  pressure 
during  inspiration,  the  whole  extent  of  the  line  traced  rising 
again  during  expiration.  The  abdominal '  type  produces 
exactly  the  contrary  effect  (Marey).     We  give  (Fig.  83)  a 

p.  normal.  Inspiration.  Expiration. 


Fig.  83.  — Abdominal  type. 

graphic  tracing  of  the  pulse,  while  respiration  is  taking  place 
during  forcible  contraction  of  the  diaphragm.  We  see  that 
in  the  abdominal  type  (as  in  the  thoracic)  the  pulsation 
diminishes,  and,  finally,  disappears,  while  the  arterial  tension 
increases.^ 

We  may  mention,  in  conclusion,  and  rather  as  an  experi- 

^  P.  Lorain,  •'  Etudes  de  Medecine  Clinique."     Le  Fouls,  1870. 


CHEMICAL  PHENOMENA   OF  RESPIRATION.        317 

mental  curiosity  than  as  an  important  physiological  fact,  the 
influence,  in  a  contrary  direction,  which  may  be  observed  to 
exist  between  the  heart  and  the  lungs.  "  We  know  that  the 
pulsation  of  the  heart  changes  the  condition  of  the  intra- 
thoracic pressure ;  supposing  the  thorax  to  be  immovable,  the 
afl[lux  of  blood  which  takes  place  at  each  diastole,  should 
compress  the  air  in  the  lungs,  and,  if  the  glottis  is  open,  give 
lise  to  a  slight  expiration ;  in  the  same  manner,  when  the  heart 
is  suddenly  emptied,  the  blood  which  gushes  out  of  the  thorax 
is  replaced  by  a  certain  quantity  of  air  which  enters  through 
the  trachea.  In  the  normal  condition,  we  are  scarcely  sen- 
sible of  this,  on  account  of  the  constant  modifications  pro- 
duced by  respiration  in  the  respiratory  capacity  of  the  thorax. 
The  fact,  however,  can  easily  be  made  plain,  by  placing  the 
trachea  of  a  dog  in  communication  with  the  registering  ap- 
paratus, and  then  puncturing  or  severing  the  medulla 
oblongata  of  the  animal  by  a  single  stroke :  respiration  ceases 
immediately,  while  the  heart  continues  to  beat  for  some 
minutes,  its  pulsations  being  registered  through  the  medium 
of  the  air  in  the  trachea  "  (P.  Bert). 

IV.    Chemical  Phenomena  of  Respiration. 

We  understand  how  the  air  and  the  blood  are  brought  into 
contact  with  each  other,  and  also  by  what  mechanism  they 
are  constantly  renewed ;  we  have  now  to  examine  the  gas- 
eous exchanges  which  are  produced  by  this  contact  taking 
place  in  the  lungs :  what  these  are  we  shall  see  by  ascertain- 
ing the  changes  made  in  the  air  and  in  the  blood,  during  their 
passage  through  the  lungs. 

A.  Modifications  in  the  air  exhaled. 

We  know  that  10  cubic  metres  (10,000  litres)  of  air  are 
received  into  the  lungs  daily,  and  that  nearly  an  equal  quan- 
tity is  expelled :  we  thus  retain  about  -^  or  ^^j  of  the  air 
inhaled ;  at  the  first  examination,  however,  the  exhaled  gas 
is  found  undiminished  in  quantity,  on  account  of  the  vapor 
contained  in  it,  which  occupies  a  considerable  space.  A  still 
more  important  change  which  takes  place  in  the  air  is  the 
loss  of  oxygen^  which  is  replaced  in  a  great  measure  by  car- 
bonic acid^  one-fifth  of  the  amount  of  the  10  cubic  metres  of 
air  inhaled  is  oxygen  (21  parts  of  O.  to  79  parts  of  N.)  ;  this 
is  equal  by  weight  to  2J  kilos,  of  oxygen.     In  the  air  ex- 


318  PULMONARY  MUCOUS  TISSUE. 

lialefl  in  24  hours,  only  1  kilo.  750  grras.  remains;  that  is  to 
say,  that  760  grms.  of  oxygen  have  been  retained  by  the  lungs 
(2.500  —  1.750  =1  750).  We  see  thus  that  we  retain  a  sura 
total  off  of  a  kilo,  (or  750  grms.)  of  oxygen  in  24  hours  (750 
grms.,  or  a  volume  of  500  litres). 

On  the  other  hand,  we  know  that  the  carbonic  acid  is 
found  represented  by  thousandths  only  in  the  atmospheric 
air,  the  air  which  we  breathe  (^^^u  ^^  TxyoTTir)-  The  quantity 
found  in  the  exhaled  air  is  very  large :  but  yet  it  differs,  ac- 
cording to  circumstances,  though,  on  the  average,  we  may  be 
said  to  exhale  850  grms.  of  carbonic  acid  in  24  hours  (a  volume 
of  400  litres :  in  order  to  account  for  the  diminution  of  volume 
which  we  have  observed  between  the  air  inhaled  and  that 
which  is  exhaled,  compare  these  figures  with  the  500  litres  of 
O.  absorbed.)  These  are  the  principal  facts  to  be  noted  in  re- 
gard to  the  air ;  the  other  changes  which  take  place  are  unim- 
portant. Thus  air  contains  f  parts  nitrogen  (21  of  O.,  79  of  N.), 
the  quantity  of  this  gas  inhaled  and  exhaled  is  supposed  by 
some  persons  to  be  equal :  others  maintain  that  it  varies,  and 
that,  at  times,  a  little  more  than  the  usual  quantity  is  given 
off,  showing  that  a  certain  quantity  is  excreted  by  the  lungs : 
indeed,  traces  of  ammonia  and  various  exhalations  arising 
from  nitrogenous  substances  are  frequently  met  with  in  the 
lungs,  as  well  as  the  vapors  belonging  to  all  those  volatile 
matters  which  sometimes  find  their  way  into  the  blood,  as, 
for  instance,  alcohol,  ether,  phosphorated  products,  and  palu- 
dal gases. 

B.  ModifiGotions  in  the  hlood  which  passes  through  the 
lungs. 

What  is  the  process  which  goes  on  in  the  blood  ?  Experi- 
ments have  proved,  what  our  previous  knowledge  enabled  us 
to  guess,  that  the  carbonic  acid  which  is  exhaled  arises  from 
the  venous  blood ;  the  latter  throwing  off  this  excretory  pro- 
duct, imbibes  oxygen  in  order  to  pass  into  the  state  of  arte- 
rial blood.  We  have  already  studied  the  gases  of  the  blood, 
and  have  seen  that,  from  the  point  of  view  of  respiration,  the 
blood  may  be  looked  upon  as  a  solution  of  gas,  the  blood 
globule  being  the  vehicle  of  the  oxygen,  and  the  serum  that 
of  the  carbonic  acid ;  we  have  also  found  that  the  essential 
difference  between  the  arterial  and  the  venous  blood  consists 
in  the  predominance  of  oxygen  in  the  former,  and  of  carbonic 
acid  in  the  latter. 


CHEMICAL  PHENOMENA   OF  RESPIRATION.        319 

Recent  analyses  of  the  gases  contained  in  the  blood,  give/ 

In  100  parts  of  arterial  blood  (in  a  dog)  ; 

Oxygen  —  20  parts,  carbonic  acid  —  34.8  parts. 

In  100  parts  of  venous  blood : 

Oxygen  —  12  parts,  carbonic  acid  —  47  parts. 

The  briUiant  red  color  of  the  arterial  blood  may,  perhaps, 
be  caused  by  a  chemical  action  of  the  oxygen  on  the  coloring 
matter,  or  hematine,  but  it  appears  to  be  chiefly  owing  to  a 
change  of  form :  under  the  exciting  influence  of  oxygen,  as 
well  as  under  that  of  some  other  agents  (chloride  of  sodium, 
for  instance),  the  blood  globule  becomes  flatter  and  slighter, 
and  refracts  the  light  in  a  diflerent  manner  from  that  seen 
when  it  is  under  the  influence  of  carbonic  acid ;  this  latter 
has  the  effect  of  causing  it  to  swell,  and  approach  more  nearly 
the  spherical  form. 

In  passing  through  the  lungs,  the  blood  also,  as  we  have 
seen,  gives  off*  a  certain  quantity  of  vapor  (the  quantity 
varies,  but  may  be  assumecl  to  be  at  least  300  grms.  in  24 
hours).  The  exhaled  air,  indeed,  as  it  leaves  the  lungs,  is 
nearly  saturated  with  vapor,  at  a  temperature  which  is 
nearly  that  of  the  body,  as  has  been  demonstrated  by  Gre- 
hant:  we  have  already  seen  that  if  a  half-litre  of  atmo- 
spheric air  be  inhaled,  the  expiration  which  follows  throws 
off  one-third  of  this  volume  of  pure  air  mixed  with  two-thirds 
of  vitiated  air.  The  vitiated  air,  which  has  been  for  some 
time  in  contact  with  the  bronchi,  is  of  the  same  temperature 
as  the  lungs,  and  is  thoroughly  moistened  ;  but  the  third  part 
of  pure  air  which  is  immediately  given  back  in  breathing,  not 
having  remained  sufficiently  long  in  the  respiratory  tree  to 
assume  exactly  the  temperature  of  its  walls,  it  follows  that 
the  entire  quantity  of  air  expelled  has  not  the  same  temper- 
ature as  the  body.  Grehant  has  shown,  by  very  close  experi- 
mental researches,  that,  the  temperature  of  the  exterior  air 
being  22^  (C),  that  of  the  air  exhaled  is  equal  to  35^.3  (C), 
17  expirations  a  minute:  the  exterior  temperature  being  — 
6^  (C),  that  of  the  air  exhaled  is  only  29^.8  (C.)  (Valentin). 
Grehant  has  also  shown  that  the  air  exhaled  is  surcharged 
with  vapor  at  its  own  temperature,  and  not  at  that  of  the 
body,  which  is  slightly  higher  (see  animal  heat).^ 

The  blood,  therefore,  grows  cooler  as  it  comes  in  contact 

^  Ludwig  and  his  pupils.     Archiv.  de  Pfliiger,  1872. 
2  N.  Grehant,  "  Cours  de  I'Ecole  Pratique."     Revue  des  Cours 
Scientifiques,  Novembre,  1871. 


320  PULMONARY  MUCOUS  TISSUE. 

with  the  air  of  the  lungs,  by  yielding  up  to  it  a  portion  of  its 
heat. 

This  fact  was  long  disputed ;  first,  because  direct  experi- 
ment on  the  subject  seemed  to  contradict  it :  two  thermom- 
eters, placed,  one  in  the  left  heart,  and  the  other  in  the  right, 
seemed  to  show  an  increase  of  heat  in  tlie  former  cavity,  and 
a  consequent  heating  of  the  blood  in  its  passage  towards  the 
lung :  more  careful  examination  has,  however,  led  to  an  entirely 
opposite  conclusion  (CI.  Bernard),  and  shown  that,  in  former 
experiments,  allowance  had  not  been  made  for  the  inequality 
of  thickness  in  the  coats  of  the  two  ventricles,  occasioning 
a  greater  loss  of  heat  in  the  right  ventiicle  (tlie  coats  of 
which  are  thin),  than  in  the  left  (of  which  the  coats  are 
thick).^  In  the  second  place,  the  increased  temperature  of 
the  arterialized  blood  was  looked  upon  as  the  necessary  con- 
sequence of  the  hyj^othesis  that  actual  combustion  takes  place 
in  the  lungs,  and  that  it  is  here  that  the  oxygen  absorbed 
during  inspiration  is  employed  to  consume  the  carbon  and 
produce  the  carbonic  acid  exhaled  in  expiration. 

It  is  now,  however,  proved  that  the  production  of  carbonic 
acid  in  the  blood  is  not  limited  to  the  pulmonary  surfice,  but 
occurs  in  the  whole  organism,  throughout  the  current  of  the 
circulation,  and,  more  j>articularly,  in  the  capillary  network: 
carbonic  acid  is,  indeed,  found  everywhere  in  the  venous 

*  Following  experiments  made  recently,  Heidenhain  and  Komer 
have  sought  to  prove  that  the  difference  in  temperature  between 
the  blood  of  the  left  heart  and  that  of  the  right  is  not  caused  by 
the  cooling  of  the  blood  in  its  passage  into  the  lungs.  They  main- 
tain that  the  blood  is  neither  cooled  nor  heated  in  passing  through 
the  lungs,  but  that  the  higher  temperature  of  the  right  ventricle 
is  caused  by  its  being  situated  more  immediately  in  the  phrenic 
centre,  and,  consequently,  being  in  contact  with  the  organs  con- 
tained in  the  abdominal  cavity  (the  liver,  stomach,  and  intestines), 
which  have  all  a  higher  temperature  than  that  of  the  organs  of  the 
thorax.  CI.  Bernard,  however,  opposes  this  theory  by  instancing 
those  cases  of  ectopia  (or  displacement)  of  the  heart,  in  which  the 
heart  from  its  transposition  is  not  in  contact  either  with  the  dia- 
phragm or  with  the  abdominal  viscera,  and  yet  contains  warmer 
blood  in  the  right  ventricle  than  in  the  left.  On  the  other  hand, 
the  heart  of  a  dog,  surrounded  by  its  pericardium,  and  is  in  no 
way  united  to  the  diaphragm,  floats  in  the  chest,  if  we  may  be 
allowed  the  expression;  by  changing  the  position  of  this  animal, 
the  relation  of  the  diaphragm  to  the  ventricle  is  modified,  without, 
however,  changing  the  relation  between  the  temperature  of  the 
blood  of  the  two  ventricles.     (CI.  Bernard,  Cours  de  1872.) 


CHEMICAL  PHENOMENA  OF  RESPIRATION       321 

blood,  and  only  increases  as  we  approach  the  summit  of  the 
venous  cone.  The  respiratory  phenomenon  of  the  lungs 
simply  consists  in  a  gaseous  exchange,  resembling,  more  or 
less,  the  phenomenon  of  diffusion,  but  which  is  not  combus- 
tion: combustion  takes  place  at  those  points  where  the 
tissues  of  the  organism  come  in  close  contact  with  the  blood, 
and  in  the  very  structure  of  these  tissues ;  the  arterial  blood  is 
only  the  vehicle  of  the  oxygen  to  these  tissues,  as  the  venous 
blood  is  that  which  carnes  off  the  carbonic  aoid. 

C.  Tlieory  of  respiration. 

Respiration,  therefore,  considered,  not  from  the  point  of 
view  of  the  gaseous  exchanges,  but  from  that  of  the  chemical 
phenomena  of  combustion,  of  combination  and  separation, — 
respiration  in  its  very  essence,  in  short,  —  takes  place,  not  in 
the  lung,  but  in  the  most  intimate  portions  of  the  tissues ; 
thus  the  liver,  in  which  extremely  important,  though  not 
well-defined,  chemical  phenomena  take  place,  makes  use  of 
all  the  oxygen  contained  in  the  blood  of  the  portal  vein, 
while  the  blood  which  flows  from  the  liver  exhibits  both  the 
highest  temperature  and  the  most  decided  features  of  the 
typical  venous  blood.  That  the  tissues  themselves  actually 
breathe,  in  a  chemical  sense,  is  proved  by  placing  them  in 
an  oxygenized  gaseous  medium,^  in  which  their  respiration 
may  be  seen  directly :  thus,  if  a  muscle  be  detached  from  an 
organism,  and  suspended  in  an  oxygenized  atmosphere,  it 
will  consume  oxygen,  and  exhale  carbonic  acid :  this  com- 
bustion is  still  more  intense  if  the  muscle  be  made  to  contract, 
the  reason  of  which  will  be  understood  by  referring  to  the 
physiological  study  of  the  muscle.  In  its  natural  position  in 
the  organism,  the  phenomena  of  the  muscle  are  the  same  as 
those  of  the  other  tissues ;  with  the  exception  that  the  blood 
here  performs  the  office  of  a  medium  from  which  the  living 
element  borrows  oxygen  (arteiial  blood),  and  gives  back  car- 
bonic acid  (venous  blood).  Thus  the  blood  of  the  veins  of  a 
muscle  is  much  darker,  more  venous,  in  short,  when  the 
muscle  is  contracted  than  when  it  is  in  a  state  of  entire 
repose. 

Respiration  consists,  then,  in  man  and  the  superior  animals, 
considered  in  a  general  way,  of  three  principal  parts,  three 

^  See  P.  Bert,  "  Lemons  sur  la  Respiration."     Lemons  3  and  4: 

Respiration  des  Tissus. 

21 


322  PULMONARY  MUCOUS  TISSUE. 

phenomena  closely  connected  and  dependent  upon  each  other: 
•1,  Respiration  of  the  tissues;  2,  Functions  of  the  blood  as  a 
vehicle  of  the  agents  and  of  the  gaseous  products  of  the 
respiration  of  the  tissues ;  3,  Gaseous  exchanges  of  the  blood 
at  the  pulmonary  surfice.  Modern  investigation  has  thrown 
great  light  on  the  inner  phenomena  composing  each  of  these 
great  acts,  the  study  of  which,  in  the  series  of  organized 
beings,  clearly  shows  their  relative  importance. 

1.  Hesjnration  of  the  Tissues.  We  have  already  spoken 
several  times  of  the  respiration  of  the  tissues  (see  pp.  320  and 
321)  :  as  the  anatomical  elements  breathe  when  separated,  so 
we  see  that  inferior  organisms,  the  mono-cellular  animals, 
breathe  directly  in  the  medium  in  which  they  are  placed,  just 
as  the  tissues  breathe  in  the  blood.  A  strange  feature  con- 
sists in  the  existence  of  certain  animals,  of  complex  structure, 
the  histological  elements  of  which  breathe  directly  in  the  air: 
such  are  the  insects  and  articulated  animals  in  general.  In 
these- the  exterior  air  is  brought  in  contact  with  each  histo- 
logical element  by  means  of  a  number  of  small  and  very 
minutely  ramified  tubes  {tracheae).,  so  that  there  is  no  inter- 
medium between  the  tissues  and  the  respirable  gaseous 
medium ;  so  in  these  animals  there  is  no  need  of  a  very 
active  circulation  of  the  blood,  which  is  not  intended  as  a 
medium  for  respiration,  but  simply  a  nutritive  fluid  in  which 
the  tissues  are  steeped. 

The  interior  phenomenon  constituting  the  respiration  of 
the  tissues  is  oxidation.,  or  combustion.,  in  short.  In  regard 
to  this,  we  must  first  show  in  what  consists  the  essential 
difference  between  the  respiration  of  the  animal  and  vege- 
table tissues. 

The  respiration  of  the  vegetable  tissues  consists  in  reduc- 
tion (at  least  during  the  day,  and  under  the  influence  of  the 
solar  light) ;  vegetables  absorb  carbonic  acid,  which  they 
reduce,  in  order,  with  the  addition  of  water,  to  form  hydro- 
carbons; by  reducing  also  the  water  absorbed,  they  form 
fatty  substances ;  they  also  absorb  oxidized  compositions  from 
sulphur,  which  they  reduce,  in  order  to  form  the  sulphides 
of  allyl,  for  instance  (in  garlic) ;  they  absorb  in  like 
manner  the  nitrates,  which  they  reduce  to  form  albumi- 
noids. All  these  phenomena  of  reduction  occasion  the 
evolution  of  oxygen,  and  accumulate  in  the  vegetable  tissues 
what  are  called  forces  of  tension ;  in  other  words,  these 
tissues  store  up  the  solar  heat,  and  employ  the  latter  to  pro- 


CHEMICAL  PHENOMENA   OF  RESPIRATION.       323 

duce  the  reductions  which  we  have  mentioned,  and  again  this 
heat  may  be  transformed  into  vis  viva,  when  the  combustion 
of  the  vegetable  tissues  takes  place. 

This  is  precisely  the  office  performed  by  animals,  whose 
tissues  consume  the  elements  furnished  by  the  vegetable 
kingdom,  oxidize  and  decompose  them  into  carbonic  acid  and 
water,  thus  producing  heat  and  force  (two  synonymous  or 
equivalent  words:  see  p.  78,  mechanical  equivalent  of  heat). 
The  interior  phenomena  of  nutrition  oxidize  carbon,  hydro- 
gen, and  sulphur :  nitrogen  apparently  yields  less  readily  to 
this  organic  oxidation,  and  the  urea,  which  represents  the  6nal 
product  of  combustion  of  the  albuminoids,  contains  nitrogen 
which  is  in  a  free  state,  or  at  least  not  combined  with  oxygen, 
because  the  urea  is  estimated  by  decomposing  it  into  car- 
bonic acid  and  nitrogen^  (by  means  of  Millon's  reagent, — 
Grehant;  ^qq '-'■  Physiology  of  the  kidney''''). 

2.  The  Office  of  the  Blood  in  Bespiration, — In  those  animals 
which  are  ranked  in  a  higher  class  than  that  of  the  articulata, 
tlie  blood  serves  as  an  intermedium  between  the  tissues 
and  the  respirable  mediums.  It  cannot,  however,  be  said  that 
the  blood  breathes  for  the  tissues;  it  neitlier  consumes 
oxygen,  nor  produces  carbonic  acid,  but  is  loaded  with  these 
gases,  simply  for  the  purpose  of  furnislung  the  tissues  with 
the  former,  and  carrying  the  latter  to  those  surfaces  by  which 

^  "  By  comparing  the  general  laws  of  nutrition  of  vegetables 
and  animals,  we  find  that  the  phenomena  of  nutrition  are  not  alike 
in  the  two  kingdoms,  but  that  they  depend  upon  each  other  in 
exact  proportion  to  their  dissimilarity."  (Wundt,  "  Physiologic.") 
The  plant  (the  green  parts)  forms  a  combustible  material  which  the 
animal  consumes:  it  operates  by  way  of  synthesis,  being  an  appa- 
ratus for  reduction  which  rejects  the  oxygen.  The  animal  takes 
from  the  plant,  either  directly  (as  the  herbivora)  or  indirectly  (as 
the  carnivora),  the  carbonates  and  other  substances,  and  consumes 
tliese.  The  animal  works  by  analysis,  and  is  an  apparatus  for 
oxidation.  By  means  of  this  series  of  metamorphoses  matter 
passes  from  the  inorganic  to  the  vegetable  kingdom,  and  thence 
back  into  the  animal  kingdom,  and  again  returns  to  the  Inorganic 
kingdom:  earth  and  air,  plant  and  animal,  earth  and  air,  forms  an 
unbroken  chain:  such  is  the  rotation  of  matter.  It  must  not,  how- 
ever, be  supposed  that  there  is  no  exception  to  this  rule,  for  reductions 
are  sometimes  observed  in  animal  organisms,  as  well  as  oxidations 
in  vegetable  organisms:  neither  is  there  any  well-defined  boundary 
existing  between  the  two  kingdoms.  (See,  on  this  subject,  "-  La 
Circulation  de  la  Vie,"  by  J.  Moleschott,  French  translation 
Paris,  1866.) 


324  PULMONARY  MUCOUS  TISSUE. 

it  is  to  be  expelled.  In  the  foetus  this  intermediary  function 
is  twofold :  the  blood  of  the  foetus  does  not  make  the  ex- 
changes directly  with  the  exterior  air;  it  receives  oxygen, 
and  gives  out  carbonic  acid,  only  indirectly,  through  the 
blood  of  the  mother ;  it  has,  by  means  of  the  placenta,  one 
more  station  of  transit  between  the  tissues  and  the  exterior 
air  than  in  the  adult  life. — The  means  by  which  the  elements 
of  the  blood  serve  as  the  vehicle  for  oxygen  and  carbonic 
acid  has  already  been  sufficiently  indicated  in  our  preceding 
study  (red  globules  of  the  blood  and  their  hemato-crystalline ; 
th^  serum  and  its  salts,  see  pp.  122  and  130). 

The  perfect  condition  of  the  blood  globule,  which  indicates 
the  capacity  of  the  blood  to  absorb  oxygen,  thus  has  an  effect 
on  the  phenomena  of  oxidation  ;  and  the  products  of  combus- 
tion, therefore,  vary  in  quulity,  and  even  in  quantity,  in  a 
corresponding  manner.  This  Ritter  especially  sought  to 
decide  by  studying  the  chemical  modifications  through  which 
the  secretions  pass  lohen  under  the  influence  of  agents  which 
augment^  annihilate^  or  modify  the  capacity  of  the  globule  for 
the  absorption  of  oxygen.  He  studied  the  effect  produced 
by  the  following  compounds:  oxygen^ protoxide  of  nitrogen^ 
oxide  of  carbon^  compounds  of  antimony  and  arsenic^  phos- 
phorus and  the  salts  of  soda,  and  the  acids  of  the  bile.  These 
substances  are  divided  into  two  classes*,  according  to  their 
action  on  the  blood  globule :  the  first  includes  oxygen,  the 
protoxide  of  nitrogen,  and  the  oxide  of  carbon.  These  three 
agents  do  not  destroy  the  form  of  the  globule ;  it  is  never 
dissolved  under  tlieir  influence,  nor  does  it  form  any  hemo- 
globine  crystals.  The  second  class,  on  the  other  hand,  con- 
sists of  substances  which,  whether  the  quantity  be  large  or 
small,  materially  alter  the  shape  of  the  globule,  and  give  rise 
to  the  a{)pearance  in  the  blood  of  the  animal  of  the  crystals 
which  are  the  distinguishing  sign  of  hemoglobine.  The  com- 
position of  the  urine  is  connected  with  the  perfect  physiolo- 
gical condition  of  the  blood  globule.  When  any  serious 
change  occurs  in  the  blood  globule,  and  especially  when  the 
crystals  of  hemoglobine  appear,  the  urine  is  found  to  contain 
abnormal  principles,  which  are  usually  the  coloring  matters 
of  the  bile  and  albumen.  Under  these  circumstances  the 
urine  resembles  that  observed  in  a  fever.^ 


1  Ritter,  "  Des  Modifications  Chimiques  que  subissent  les  Se- 
cretions sous  I'Influence  de  quelques  Agents  qui  modifient  les 
Globules  Sanguins."     Paris,  1872. 


CHEMICAL  PHENOMENA   OF  RESPIRATION.       325 

To  these  researches  must  be  added  those  of  Manass<^in,  as 
to  the  dimensions  of  the  red  globules  of  the  blood  under 
different  circumstances.  Manassein  has  recognized  the  fact 
that  the  dimensions  of  the  red  globules  are  least,  when,  from 
a  pathological  increase  of  activity,  these  globules  are  in  a 
condition  to  yield  an  exaggerated  amount  of  oxygen  (as  in 
fever),  or  in  any  condition  which  increases  the  difficulty  of 
absorption  (as  when  under  the  influence  of  carbonic  acid  and 
morphine)  ;  on  the  other  hand,  they  increase  in  size  when- 
ever they  are  brought  in  contact  with  any  medium  which 
contains  a  larger  amount  of  oxygen,  or  are  placed  under  any 
circumstances  which  tend  to  check  the  loss  of  oxygen  (as 
when  under  the  influence  of  refrigerants,  quinine,  alcohol, 
hydrocyanic  acid).^ 

The  blood  acting  as  the  vehicle  of  the  oxygeij,  the  more 
blood  an  animal  possesses,  the  larger  reserve  of  oxygen  it 
will  have  in  its  circulating  reservoir,  and,  consequently,  will 
longer  be  capable  of  supporting  the  privation  of  air;  thus, 
an  animal  which  has  lost  a  large  quantity  of  blood  cannot 
long  exist  without  constant  renewal  of  oxygen,  owing  to  the 
fact  that,  in  losing  the  globules  of  the  blood,  it  has  lost  the 
oxygen  which  was  stored  up  in  them.  The  power  of  resist- 
ance to  suffocation  exhibited  by  some  animals  has  long 
seemed  inexplicable :  in  the  case  of  the  diving  animals,  how- 
ever, Paul  Bert  has  shown  that  this  power  is  simply  owing 
to  their  possessing  a  larger  quantity  of  blood :  thus  a  duck 
possesses  one-third,  or  even  one-half  more  blood  than  a  land 
fowl  of  the  same  weight ;  if  the  latter  be  immersed  in  water 
(or  strangled),  it  dies  in  two  or  three  minutes,  while  the 
fonner  will  hold  out  for  seven  or  eight  minutes.  This  power 
of  supporting  the  privation  of  air  is  due  to  the  large  quantity 
of  blood  possessed  by  the  animal,  which  forms  a  sort  of 
storehouse  of  oxygen  in  combination  (P.  Bert,  op.  cit.) 

3.  Function  of  the  Pulmonary  Surface.  —  The  blood, 
which  may  be  considered  as  the  intermedium  between  the 
tissues  and  the  respirable  medium,  may  be  also  the  seat  of 
gaseous  exchanges  over  the  whole  surface  which  comes  in 
contact  with  this  medium.  Thus,  in  the  frog,  respiration  takes 
place  by  means  of  the  surface  of  the  skin  as  well  as  by  the 
mucous  surface  of  the  lungs.  If  the  mesentery  of  a  batrachian 
be  stretched  out,  and  the  circulation  examined,  the  contents 

'  See  an  excellent  epitome  of  Manassein's  researches,  by  E. 
Lauth,  in  "  Gazette  Medicale  de  Strasbourg."     ler  aout,  1872. 


326  PULMONARY  MUCOUS  TISSUE. 

of  the  mesenteric  Veins,  which  were  dark  colored  at  the  be- 
ginning of  the  operation,  are  soon  observed  to  become  bright 
red,  like  arterial  blood ;  this  is  because  oxygenation  has  been 
effected  simply  by  the  exposure  to  air,  both  of  the  surface  of 
the  mesentery,  and  of  the  intestine  during  the  experiment ; 
and  the  frog,  thus  prepared,  breathes  (in  the  pulmonary  or 
respiratory  sense  of  the  word)  through  the  lungs,  the  skin, 
and  the  mesentery.  In  speaking  of  the  epithelium  of  the 
lungs,  we  have  already  mentioned  that  oxygenation  goes 
on  in  the  intestinal  mucous  of  the  cobitis  fossilis  (water 
loach).  Finally,  the  skin  of  the  superior  animals,  and  even 
of  man,  appears  to  have  some  share  in  the  exchanges  effected 
by  respiration  between  the  blood  and  the  outer  air,  especially 
in  respect  to  exhalation  ;  we  shall  return  to  this  subject  when 
studying  the  functions  of  the  cutaneous  surface. 

These  exchanges,  however,  for  the  most  part,  are  made 
on  one  particular  surface,  which,  in  the  case  of  those  animals 
which  live  in  the  air,  is  represented  by  the  luugs.^  The 
lungs  are  the  organ  of  respiration,  insomuch  as  they  are  the 
place  in  which  exchange  goes  on  between  the  blood  and 
the  outer  air :  respiration  has  been  hitherto  studied  from  this 
point  of  view,  but  our  present  knowledge  of  the  subject 
allows  us  to  regard  the  pulmonary  fmiction^  not  as  the  only 
seat  of  respiration,  but  as  representing  a  link,  and  as  one  of 
the  least  important,  in  the  long  chain  of  processes  which, 
beginning  in  the  very  depth  of  the  histological  elements, 
terminate  in  those  surfaces  which  come  in  contact  with  the 
external  medium. 

The  function  of  the  pulmonary  surface  can  thus  be  fully 
understood  only  in  the  light  of  the  recent  acquisitions  of 
physiology;  and  the  history  of  respiration  offers  a  most 
singular  collection  of  hypotheses  formed  on  this  subject  by 
physiologists  and  physicians:  some  maintaining  that  the 
pulmonary  respiration  has  only  a  mechanical  office,  by  which 

^  These  exchanges  take  place  in  the  epithelium  of  the  bronchi, 
as  well  as  in  that  of  the  alveoli.  The  columnar  epithelium  of  the 
bronchial  mucous  readily  allows  the  production  of  hematosis  (o/ 
pulmonary  gaseous  exchanges).  In  order  to  prove  this,  we  need 
only  remember  the  anatomical  fact  that  the  bronchial  arteries  hate 
no  corresponding  veiiis,  and  that  their  blood,  having  nourished  the 
bronchi,  becomes  oxidized  by  contact  with  the  air,  and,  conse- 
quently, flows  immediately  into  the  pulmonary  veins,  which  latter 
bring  it  back  to  the  heart  with  the  general  mass  of  the  blood  that 
has  become  arterial  blood. 


CHEMICAL  PHENOMENA   OF  RESPIRATION.       327 

the  blood  passes  through  the  vessels  of  the  lung,  owing  to  the 
expansion  of  the  latter ;  while  others  hold  that  its  function  is 
entirely  physical,  and  consists  in  cpoli?ig  the  blood  by  contact 
with  the  air.  This  cooling  does  take  place,  as  we  have  said, 
but  i  t  is  a  secondary  process,  and  of  scarcely  any  importance 
(CI.  Bernard).  Only  a  small  proportion  of  the  cold  air  which 
enters  the  respiratory  tree  at  each  respiration  penetrates  as 
far  as  the  pulmonary  lobules,  and  that  only  after  it  has  been 
warmed.  The  larger  part  of  the  air  inhaled  is  confined  to 
the  respiratory  organs,  the  nasal  chambers,  the  pharynx,  and 
the  large  bronchi.  Lavoisier  was  the  first  to  furnish  any 
certain  knowledge  as  to  the  process  of  respiration ;  confirm- 
ing the  ideas  entertained  by  J.  Mayow,^  in  regard  to  his 
spritus  igno-aereus.  Lavoisier  showed  that  respiration  was  a 
process  of  combustion,  but  did  not,  however,  determine  the 
exact  seat  of  the  combustion:  Lagrange,  Spallanzani,  and 
William  Edwards  proved  that  these  oxidations  take  place 
in  the  tissues,  and  that  the  lungs  are  only  the  place  from 
which  the  gaseous  products  of  these  interior  combustions  are 
exhaled. 

It  is  not,  however,  sufiicient  to  know  that  the  blood  in  the 
lungs  simply  evolves  carbonic  acid,  and  imbibes  oxygen ;  the 
necessary  conditions  of  this  interchange  must  be  distinctly 
stated.  First,  in  regard  to  the  oxygen,  we  already  know 
that  this  gas  is  not  dissolved  by  the  blood,  but  is  absorbed 
by  the  red  globules  (Hematocrystalline).  Neither  is  the 
exhalation  of  the  carbonic  acid  produced,  as  might  be  at  first 
supposed,  simply  by  a  diffusion  of  the  gas,  or  by  the  evolution 
of  dissolved  gas  in  an  atmosphere  containing  very  little  of 
the  gas.  The  air  of  the  pulmonary  vesicles  contains  actually 
8  per  cent  of  CO'^,  which  is  a  condition  unfavorable  to  the 
evolution  of  the  carbonic  acid  of  the  blood ;  while,  on  the 
other  hand,  a  portion  of  the  latter  is,  not  dissolved,  but  com- 
bined with  the  salts  of  the  serum  (carbonates  and  phosphates. 
Emile  Fernet.  See  p.  129).  It  is,  therefore,  probable,  that 
■  some  process  takes  place  in  the  lungs,  the  eflfect  of  which  is 
to  forcibly  expel  the  carbonic  acid;  this  process  is  undoubt- 
edly chemical  in  its  nature,  and  some  experiments  seem  to 
show  that  it  somewhat  resembles  that,  by  means  of  which 
the  acids  evolve  carbonic  acid  from  the  carbonates.  These 
facts  gave  rise  to  the  theory  formed  by  Robin  and  Verdeil  as 

1  See   Gavarret,   *'  Les    Phenomenes    Physiques  de  la  Vie." 
Paris,  1869. 


8*48  PULMONARY  MUCOUS  TISSUE. 

to  the  existence  oi  a.  pneumic  acid  (see  p.  128)  ;  the  existence 
of  this  acid  has  not  been  confirmed ;  and,  moreover,  it  has 
been  observed  that  whenever,  in  the  course  of  experi- 
ments, the  oxygen  mingh^s  with  the  venous  blood,  even  in 
vitro,  carbonic  acid  is  immediately  evolved :  this  leads  us  to 
imagine  that  the  combination  of  the  oxygen  and  the  globule 
(oxy-hemoglobin,  the  spectroscopic  features  of  which  we 
have  already  studied,  p.  110),  possesses  properties  similar  to 
those  of  an  acid,  and  thus  occasions  the  evolution  of  carbonic 
acid  from  the  venous  blood.  The  absoi-ption  of  oxygen  is 
thus  doubly  important  in  respiration,  both  for  its  own  sake, 
and  as  the  cause  of  the  evolution  of  the  carbonic  acid  pre- 
viously formed. 

D.  Asphyxia, 

The  preceding  remarks  will  enable  ns  to  point  out,  in  a  few 
"words,  the  various  methods  by  which  asphyxia  may  be  pro- 
duced. Asphyxia  may  be  caused,  either  by  deprivation  of 
respirahle  air,  or  by  intoxication,  that  is  to  say,  by  the 
absorption  of  any  pernicious  gas.^ 

a.  Asphyxia,  caused  by  absence  of  respirahle  air,  may  be 
produced  in  two  ways,  —  either  by  there  being  no  oxygen  to 
be  absorbed,  —  or  by  the  carlxjnic  acid  being  no  longer 
evolved  from  the  blood. 

1.  Animals  die  in  an  atmosphere  which  is  not  constantly 
renewed  by  the  admission  of  fresh  air,  when  they  have  ex- 
hausted the  greater  portion  of  the  oxygen,  provided  that  the 
carbonic  acid  formed  be  taken  away,  in  order  to  avoid  the 
inconvenience  produced  by  its  accumulation;  reptiles  die 
when  all  the  oxygen  is  exhausted,  the  mammifera  when  only 
2  per  cent  remain ;  and  birds,  when  there  is  only  4  or  3  per 
cent  of  the  quantity  left  (Paul  Bert).  These  facts  explain 
the  feeling  of  distress  experienced  by  aeronauts  and  by  trav- 
ellers who  ascend  high  mountains:  the  diminution  of  the 
extenial  pressure  produces  the  same  effect  as  rarefaction  of 
the  oxygen;  respiration  is,  consequently,  performed  with 
difficulty,  and  there  is  a  lack  of  oxygen  for  the  purpose  of 
keeping  up  combustion,  and  for  producing  heat  and  force; 
fatigue,  chill,  and  a  tendency  to  sleep,  follow.  These  effects 
are  produced  in  an  exaggerated  degree  while  ascending 
mountains,  because  the  traveller  is  then   obliged    to  exert 

*  See  "  Nouveau  Diet,  de  Med.  et  de  Chirurgie,"  Vol.  III.  art 
Asphyxie,  par  P.  Bert. 


CHEMICAL  PHENOMENA  OF  RESPIRATION.       329 

considerable  muscular  force.  These  different  symptoms, 
especially  the  lowering  of  the  temperature,  appear,  however, 
to  come  from  another  cause,  which  can  only  be  explained 
by  means  of  the  knowledge  recently  acquired  as  to  the 
-mechanical  equivalent  of  heat  (see  p.  79).  L.  Lortet,  who 
has  studied  the  mountain  sickness^  {77ial  des  montagnes), 
by  the  aid  of  almost  every  registering  instrument  now 
employed  in  physiology  (the  sphygmograph,  the  anapno- 
graph,  special  thermometers,  etc.),  attributes  the  cooling  of 
the  body  to  the  fact  that  the  internal  combustion  is  unable  to 
maintain  the  previous  temperature,  which  has  to  contend  at 
once  against  the  external  cold,  and  tjie  loss  of  the  heat  which 
is  being  transformed  into  muscular  effort :  in  short,  the  in- 
tensity of  the  respiratory  combustion  increases  in  proportion 
to  the  force  expended  (Gavarret) ;  heat  is  transformed  into 
mechanical  force,  sufficient  heat  being  formed  for  this  pur- 
pose, in  accordance  with  the  density  of  the  air  and  the 
quantity  of  oxygen  inhaled.  "  In  ascending  mountains,  how- 
ever, and  especially  when  at  a  great  height,  and  on  declivities, 
where  the  labor  of  ascent  is  very  great,  an  enormous  quantity 
of  heat  is  required  to  be  transformed  into  muscular  force. 
This  expense  of  force  consumes  more  heat  than  the  organism 
can  furnish;  consequently  the  body  grows  sensibly  colder, 
rendering  frequent  halts  necessary,  for  the  purpose  of  recov- 
ering warmth.  During  the  process  of  digestion  chill  is 
scarcely  perceptible:  consequently  the  guides  advise  trav- 
ellers to  take  food  once  in  every  two  hours,  or  thereabouts." 

These  facts  serve  to  explain  the  effect  produced  on  the 
health  and  pathology  of  the  inhabitants  of  high  mountains, 
caused  by  the  feeble  pressure  of  the  atmosphere  in  which 
they  live.  These  men,  as  has  been  shown  by  Jourdanet, 
exist  in  an  atmosphere  containing  an  insufficient  quantity  of 
oxygen  :  they  are  anoxyhematics} 

2.  If  an  animal  be  shut  up  in  a  confined  space,  and  a  suffi- 
cient quantity  of  oxygen  be  admitted,  while  the  carbonic  acid 
produced  by  respiration  is  allowed  to  accumulate,  ^Ae  animal 
mill  die,  as  soon  as  the  proportion  of  this  gas  becomes  too 
great;  the  time  needed  to  produce  this  effect  differs  greatly 


1  L.  Lortet,  "  Deux  Ascensions  au  Mont-Blanc  en  1869,  Re- 
cherches  Physiologiques  sur  le  Mai  des  Montagues."  Paris, 
Victor  Massou,  1869  ;  and  "  Revue  des  Cours  Scieutifiques.'^ 
1869-70. 

1  Jourdanet,  "  Le  Mexique  et  rAm6rique  Tropicale."  Paris, 
1864. 


830  PULMONARY  MUCOUS  TISSUE. 

in  different  animals.  Not  that  carbonic  acid  is  a  poison^  but 
only  that  the  excess  of  this  gas  (or  its  too  great  pressure)  in 
the  air,  hinders  the  egress  of  thnt  which  is  in  the  blood ;  the 
blood  is  tlnis  prevented  from  collecting  the  gas  evolved  from 
the  combustion  of  the  tissues,  and  the  respiration  of  the  latter 
becomes  impeded. 

In  the  case  of  asphyxia  in  a  confined  atmosphere,  both  the 
causes  which  we  have  mentioned  are  found  to  exist ;  diminu- 
tion of  oxygen  and  increase  of  carbonic  acid.  Both  occur, 
but  in  different  and  varying  proportions.  By  means  of 
numerous  experiments,  which  we  have  not  space  to  describe, 
Paul  Bert  has  reached  the  conclusion  that  death  in  a  con- 
fined air  is  caused,  in  warm-blooded  animals,  by  the  want  of 
oxygen,  and,  in  cold-blooded  animals,  by  an  excess  of  car- 
bonic acid.^ 

In  a  natural  death,  whatever  be  the  cause,  the  blood, 
arterial  as  well  as  venous,  loses  all  its  oxygen.  Tliis  is  why 
Paul  Bert  pronounces  the  somewhat  paradoxical  opinion  that 
"  death  is  always  owing  to  asphyxia." 

b.  The  type  of  asphyxia  by  intoxication  is  asphyxia  by 
carbonic  oxide ;  this  gas  constitutes  the  poisonous  agent  in 
cases  of  asphyxia  from  the  fumes  of  charcoal  (Leblanc).  Here, 
the  red  globule  is  first  affected ;  we  have  already  seen,  in 
studying  the  spectroscopic  features  of  the  blood  (p.  119), 
that  the  carbonic  oxide  takes  the  place  of  oxygen  in  the 
hemoglobin,  and  we  can  easily  imderstand  that  this  oxy- 
carbonized  hemoglobin  is  no  longer  fit  to  keep  up  the 
combustion  of  the  tissues;^  thus  in  asphyxia,  by  means  of 
carbonic  oxide,  the  temperature  is  lowered  (CI.  Bernard). 
We  find,  in  short,  that  this  asphyxia  consists  in  the  depriva- 

^  See  Paul  Bert,  "Lemons  sur  la  Respiration."  Lemons  27 
and  28. 

2  This  intoxication  is  effected  with  remarkable  rapidity.  Gre- 
hant's  experiments  on  dogs  show  that  in  an  animal  breathing  air 
containing  one-tenth  of  carbonic  oxide,  the  arterial  blood,  between 
the  tenth  and  the  twenty-fifth  second,  contains  4  per  cent  of  car- 
bonic oxide,  and  only  14  per  cent  of  oxygen;  and  that,  in  a  space 
of  time  varying  from  one  minute  and  fifteen  seconds  to  one  minute 
and  thirty  seconds,  a  large  proportion  (18.4  per  cent)  of  carbonic 
oxide  appears  in  the  blood,  while  the  quantity  of  oxygen  diminishes 
until  it  is  reduced  to  4  per  cent.  We  may  therefore  conclude,  with 
Grehant,  that,  from  the  first  moment  that  a  man  enters  an  atmos- 
phere which  is  heavily  laden  with  carbonic  oxide,  the  poison  of  this 
gas  is  absorbed  by  the  arterial  blood,  or,  in  other  words,  almost 
instantly  takes  the  place  of  oxygen  in  the  globule,  rendering  it 
incapable  of  absorbing  oxygen. 


CHEMICAL  PHENOMENA  OF  RESPIRATION.       331 

tion  of  oxygen ;  this  deprivation,  however,  works  by  means 
of  another  mechanism  than  that  ah-eady  mentioned ;  being 
simply  due  to  the  fact  that  the  blood  has  lost  its  power  of  act- 
ing as  the  vehicle  of  the  gas.  The  carbonic  oxide  does  not 
exert  its  poisonous  influence  directly  upon  the  tissues  :  Paul 
Bert  has  shown  that  the  presence  of  this  gas  lias  no  eflect 
upon  the  gaseous  exchanges  constituting  the  elementary 
respiration  of  the  tissues,  when  in  contact  with  the  oxygen. 

Some  gases  act  directly  on  the  anatomical  elements  as 
poisonbus  substances ;  in  such  cases  asphyxia,  properly  so- 
called  when  speaking  o^  respiration^  does  not  take  place,  but 
a  poisoning  is  produced  by  a  gaseous  agent :  as,  for  instance, 
compounds  of  cyanogen. 

Paul  Bert's  researches  on  the  subject  of  the  influence  of 
compressed  air  have  led  to  the  discovery  of  the  singular  and 
unlooked-for  fact,  that  if  oxygen  be  sufficiently  condensed  it 
becomes  poisonous.  If  an  animal  (a  dog,  for  instance)  be 
placed  in  pure  oxygen,  at  an  atmospheric  pressure  of  5  or  6, 
or,  what  amounts  to  the  same  thing  in  ordinary  air,  at  a  pres- 
sure of  20  atmospheres,  it  exhibits  the  most  alarming  symp- 
toms, consisting  in  attacks  of  clonic  convulsions  similar  to 
those  produced  by  strychnine.  These  effects  begin  to  appear 
at  the  moment  when  the  arterial  blood  of  the  dog,  instead  of 
the  normal  proportion  of  18  to  20  cubic  centims.  of  oxygen 
to  100  cubic  centims.,  contains  only  from  28  to  30.  If  the 
])roportion  reaches  35  cubic  centims.,  death  usually  follows. 
It  is  remarkable  that  the  convulsive  movements  continue 
after  the  animal  has  been  placed  again  in  the  fresh  air,  and 
after  the  blood  has  been  restored  to  its  normal  condition. 
This  seems  to  show  that,  under  the  influence  of  this  remark- 
able hyper-oxidation  of  the  hemoglobuline,  a  poisonous  prod- 
uct is  formed  in  the  blood,  the  effects  of  which  resemble 
those  produced  by  strychnine  or  carbolic  acid.^ 

E.   General  results  of  respiration. 

The  gaseous  interchange  in  the  lungs  is  thus  only  the 
result  of  the  products  of  the  partial  respiration  (combustion) 
which  takes  place  in  the  different  departments  of  the  organ- 
ism :  since  to  breathe  is  to  live  and  to  perform  the  functions 
of  life,  the  measure  of  the  life  and  energy  of  the  working  of  the 
organism  in  general  will  give  the  amount  of  the  pulmonary 
gaseous  exchanges.     Under  different  circumstances  consider- 

^  Paul  Bert,  "  Comptes-rendus  de  rAcademie  des  Sciences." 
1872-73. 


832  PULMONARY  MUCOUS  TISSUE. 

able  variation  is  observed  in  the  quantity  of  oxygen  absorbed 
and  carbonic  acid  exhaled  ;  these  exchanges  have  been  shown 
to  be  in  direct  proportion  to  the  activity  of  the  organs ;  they 
are  greater  in  wakefulness  than  during  sleep ;  alter  eating, 
more  oxygen  is  absorbed,  and  more  carbonic  acid  exhaled ; 
movement,  and  muscular  labor  in  general,  increase  these  ex- 
changes to  their  highest  point ;  intellectual  labor,  likewise, 
increases  them,  as  the  nerve  globules,  and  the  nervous  ele- 
ments in  general,  consume  oxygen  like  all  other  elements, 
especially  when  they  are  at  work. 

The  nervous  tissue  may  be  said  to  require  the  largest 
quantity  of  oxygen,  that  is,  of  arterial  blood ;  the  first  symp- 
toms of  asphyxia  are  agitation  of  the  nerves,  ringing  in  the 
ears,  dimness  of  sight,  mental  disturbance,  and  loss  of  con- 
sciousness, all  which  begin  in  the  cephalic  part  of  the  cerebro- 
spinal system ;  reflex  actions  of  a  medullary  nature  are  also 
produced  (motions  resembling  those  made  in  self-defence,  in 
flight,  and  in  swimming;  also  excretion  of  the  fecal  matters, 
the  urine,  the  spermatic  fluid,  etc.),  but  these  quickly  dis- 
appear. It  seems  that,  at  the  moment  when  asphyxia  takes 
place,  the  carbonic  acid  accumulated  in  the  blood  acts  upon 
the  nervous  centres  and  excites  them ;  thus  we  find  certain 
physical  acts,  such  as  the  memory,  under  these  circumstances 
carried  to  the  highest  degree ;  this  occurs  in  the  case  of 
persons  apparently  drowned,  who,  on  being  restored  to  life, 
state  that  at  the  moment  of  suffocation  the  memory  reached 
its  highest  point :  that  they  saw  pass  before  their  eyes  in  a 
few  seconds,  and  with  astonishing  clearness,  the  whole  pre- 
vious history  of  their  life,  many  events  which  they  supposed 
had  for  ever  been  banished  from  thought  and  memory.^  This 

*  Brown- Sdquard  long  since  drew  the  attention  of  physiologists 
to  this  exciting  action  of  carbonic  acid  (see  "  Journal  de  Physiolo- 
gie,"  1858,  and  following  years).  It  is  principally  observed  in  the 
muscles  (both  smooth  and  striated)  which  contract  strongly  in 
animals  killed  by  strangulation.  The  movements  observed  post 
mortem^  and  the  occasional  and  strange  attitudes  spontaneously 
assumed  by  corpses  (particularly  of  cholera  patients)  must  be 
ascribed  to  a  similar  cause.  CI.  Bernard  has  recently  demonstrated 
that  in  the  case  of  animals  asphyxiated  by  carbonic  acid  (strangu- 
lation), the  temperature  rises  while  the  asphyxia  lasts,  and  that  this 
increase  of  temperature  occurs  chiefly  in  the  muscular  system 
(excited,  no  doubt,  by  CO^),  and  are  produced,  as  is  always  the 
case,  by  chemical  phenomena  of  combustion,  increased  by  the  con- 
ditions of  the  asphyxia  which  are  the  cause  of  convulsions.  In 
this  case  the  muscle  entirely  consumes  the  oxygen  of  the  blood, 
which  thus  furnishes  material  for  exaggerated  phenomena,  and, 


CHEMICAL  PHENOMENA   OF  RESPIRATION^        833 

excitatim,  produced  by  an  excess  of  carbonic  acid,  appai  cntly 
is  chiefly  in  those  nervous  centres  which  govern  respiration 
(and  which  we  shall  study  shortly :  the  medulla  oblongata, 
or  bulb)  ;  the  over-excited  respiration  then  becomes  hurried, 
and  much  more  forcible  than  before,  as  is  observed  in  cases 
of  dyspnoea.  On  the  other  hand,  when  the  blood  contains  a 
large  quantity  of  oxygen,  the  (central)  desire  to  breathe 
{desoin  de  respirer)  is  less  strongly  felt,  and  respiration  ceases 
or  becomes  imperceptible :  for  instance,  if  artificial  respiration 
be  produced  in  an  animal,  in  such  a  manner  as  to  accumulate 
an  excess  of  oxygen  in  the  blood,  the  desire  to  breathe  is  no 
longer  experienced  in  the  nervous  centres  (the  medulla 
oblongata) ;  these  are  not,  in  this  case,  excited  by  the  car- 
bonic acid,  and  spontaneous  efforts  at  respiration  will  almost, 
if  not  entirely,  cease.  Similarly  let  a  man  make  several  rapid 
and  deep  inspirations:  as  the  blood  is  now  saturated  with 
oxygen,  and  contains  very  little  carbonic  acid,  a  certain  time 
will  elapse  before  the  desire  for  respiration  is  felt ;  thus  divers, 
after  making  a  number  of  rapid  and  deep  respirations,  can  re- 
main for  a  certain  time  in  the  water,  without  suffering  from 
the  complete  arrest  of  respiration. 

We  see  thus  that  the  gaseous  exchanges  have  great  influ- 
ence on  the  functions  of  the  nervous  centres,  and  especially 
of  the  respiratory  nervous  centre,  and  that  these  facts  must  be 
taken  into  account  when  studying  the  relation  between  the 
nervous  system  and  the  production  of  the  mechanical  phe- 
nomena of  respiration. 

Returning  to  the  study  of  the  conditions  which  serve  to 
increase  or  diminish  the  respiration  of  the  tissues,  or  rather, 
the  magnitude  of  the  gaseous  exchanges  which  take  place  in 
the  lungs,  we  shall  find  other  differences,  depending  on  con- 
stitution, age,  and  sex:  a  robust  person  produces  more  car- 
bonic acid  in  a  given  time  than  one  of  a  delicate  constitution ; 
a  child  produces  more  than  an  adult  of  the  same  weight;* 

consequently,  produces  calorification  (CI.  Bernard,  Cours  de  1872). 
This  explains  the  elevation  of  temperature  observed  in  corpses  a  short 
time  after  death  (especially  in  persons  who  have  died  of  cholera). 
The  fact  of  this  increase  was  formerly  disputed,  but  it  has  been 
proved  beyond  all  doubt,  and,  now  that  its  mechanism  is  explained, 
it  no  longer  appears  extraordinary. 

^  This  is  the  case  with  a  child,  but  not  with  a  new-born  infant, 
nor  yet  with  the  fcBtus.  The  combustion  which  takes  place  in  the 
tissues  of  the  latter  is  much  less  active :  thus  the  muscles  of  newly 
born  animals  consume,  in  the  same  space  of  time,  a  much  smaller 
quantity  of  oxygen  than  those  of  adult  annuals  of  equal  weight 


334  PULMONARY  MUCOUS  TISSUE. 

this  fact  is  connected  with  the  phenomena  of  development 
and  increase  of  active  life  belonging  to  the  child.  One  of  the 
most  curious  of  the  conditions  ajQTecting  the  quantity  of  car-- 
bonic  acid  exhaled  in  respiration,  is  the  influence  of  sex,  and 
of  menstruation  in  women.  The  researches  of  Andral  and 
Gavarret  show  that  the  quantity  of  carbonic  acid  exhaled  by 
man  increases  until  the  age  of  thirty  years,  and  after  that 

Eeriod  diminishes.  In  woman,  the  quantity  of  carbon  ex- 
aled  increases  up  to  the  period  of  puberty,  until  the  appear- 
ance of  the  first  catamenial  discharge:  from  this  time  it 
remains  stationary,  until  the  menopause  increases  it  for  a 
sliort  time,  after  which  it  follows  the  same  downward  course 
as  in  an  old  man.  This  is,  no  doubt,  because  at  each  cata- 
menial period  a  considerable  quantity  of  material  flows  from 
the  economy  with  the  blood.  This  material  is  not  subjected 
to  the  action  of  the  oxygen,  but  the  products  of  their  imper- 
fect combustion  are  not  eliminated  with  the  gaseous  ex- 
changes of  respiration ;  thus,  during  pregnancy,  the  menses 
being  suppressed,  the  quantity  of  carbon  exhaled  by  the 
respiratory  organs  is  considerably  increased,  diminishing  as 
menstruation  returns.^ 

The  mean  result  of  respiration  is  as  follows :  an  adult  man 
excretes  850  grms.  of  carbonic  acid  (see  p.  317)  in  24  hours, 
forming  a  volume  of  about  400  litres.  A  knowledge  of  this 
figure  is  of  practical  use,  inasmuch  as  it  shows  how  much 
pure  air  is  required  by  an  adult  man  of  average  vigor.  A 
proportion  of  yoliTr  ^^  carbonic  acid  in  the  air  inhaled  is 
admitted  to  be  injurious.  Now,  if  we  give  out  400  litres  of 
carbonic  acid  in  24  hours,  16  litres  will  be  got  rid  of  in  an 
hour,  which  is  exactly  sufiicient  to  vitiate  4  cubic  metres 

(the  proportion  being  |-|.  Paul  Bert).  By  means  of  this  dis- 
covery Paul  Bert  explains  the  resistance  to  asphyxia  in  new-bom 
animals.  It  is  a  well-known  fact  that  a  dog,  just  born,  may  be 
immersed  in  tepid  water  for  half  an  hour,  and  yet  be  taken  out 
alive;  and  it  will  resist  strangulation,  or  copious  bleeding,  etc.,  for 
a  much  longer  space  of  time.  This  circumstance  can  only  be  ex- 
plained by  supposing  that  its  circulation  still  resembles  that  of  its 
foetal  existence,  as  the  same  state  of  things  continues  even  when 
the  amount  of  blood  has  been  diminished  by  long-continued  bleed- 
ing. The  resistance  of  the  newly  born  animal  can  be  explained 
only  by  the  fact  of  a  still  greater  resistance  on  the  part  of  its  ana- 
tomical elements,  which,  consuming  less  oxygen,  can  therefore 
longer  support  the  want  of  it. 

'  Andral  et  Gavarret,  "  Recherches  sur  la  Quantite  d'Acide 
Carbonique  exhale  par  le  Poumon  dans  I'Espece  Humaine." 
(Annal.  de  Chimie  et  de  Physique.     1813.) 


REFLEX  RESPIRATION.  335 

{■fl^js  =  iAtt)-  ^^?  therefore,  require  at  least  4  cubic 
metres  of  pure  air  each  hour  we  breathe.  Taking  into 
account,  however,  the  various  combustions  and  decomposi- 
tions taking  place  around  us,  and  which  contribute  largely  to 
the  vitiation  of  the  air,  hygienists  have  doubted  the  accuracy 
of  this  figure,  and  it  is  generally  admitted  that,  in  order  to 
fulfil  all  the  requirements  of  hygiene,  a  man  needs  10  metres 
of  pure  air  evei'y  hour, 

V.   Influence  of  the  Nervous  System  on  Respiration 

1.  The  Respiratory  Nervous  Ceyitre.  —  The  mechanical 
phenomena  of  respiration  (inspiration  and  expiration)  are 
reflex  acts  of  which  the  nervous  centre  is  found  in  the  medulla 
oblongata  (bulb),  at  the  level  of  the  gray  matter  of  t'-C  fourth 
ventricle,  near  the  origin  of  the  pneumo  -  gastric  and  the 
spinal  nerves.  Galen  pointed  out  the  importance  of  this 
point,  and  the  sudden  cessation  of  res})iration  (that  is  to  say, 
of  life)  which  follows  injury  to  the  medulla  oblongata;  but 
the  investigations  of  Legallois  and  Flourens^  have  served  to 
decide  the  position  of  this  point  or  noeud  vital  more  ex- 
actly. 

This  centre  is  situated  near  those  of  the  motor  nerves  of 
the  tongue  (hypoglossal),  of  the  lips  (Inferior  ganglion  of  the 
facial  nerve),  and  of  the  cardiac  fibres  of  the  spinal  and  the 
pneumo-gastric  nerves.  JLabio-glosso-laryngeal  paralysis^ 
which  has  been  so  carefully  studied  by  Duchenne  (of  Bou- 
logne), results  from  attacks  of  these  centres  successively:  the 
tongue  is  generally  aflTected  first;  some  months  later,  the 
muscles  of  the  palate  are  attacked  ;  then  the  orbicularis' oris  ; 
followed  by  an  attack  of  suffocation  and  by  syncope.^ 

We  have  already  seen  that  the  blood  may  directly  influ- 
ence this  respiratory  centre,  according  as  it  abounds  in 
oxygen  or  in  carbonic  acid,  and,  especially,  that  an  excess  of 
carbonic  acid  coming  in  contact  with  the  gray  matter  (in  the 
4th  ventricle)  of  this  nervous  centre,  increases  to  the  high- 
est degree  the  desire  to  breathe.  The  first  respiratory  move- 
ment of  the  foetus  is,  no  doubt,  caused  by  the  sudden  inter- 
ruption of  the  placental  respiration  (see  p.  324),  producing 


^  See  Flourens,  "  Recherches  Experimentales  sur  le  Syst^me 
Nerveux."  1842,  p.  196. 

2  Duchenue  (de  Boulogne),  "  De  1' Electrisation  Localisee." 
1872,  p.  5G1. 


^6  PULMONARY  MUCOUS  TISSUE. 

in  the  blood  an  accumulation  of  carbonic  acid  which  directly 
excites  the  respiratory  nervous  centre.^  For  the  most  part, 
however,  respiration  is  caused  by  a  simple  reflex  act,  of  which 
this  gray  matter  forms  the  centre ;  the  consideration  of  which 
leads  us  to  consider  the  centripetal  and  the  centrifugal 
nerves. 

2.  The  Centripetal  Paths.  —  The  centripetal  nerves  of  res- 
j»iration  are  first  the  pneumo-gastric,  leading  to  the  medulla 
oblongata  at  the  vital  point ;  to  these,  however,  must  be 
added  the  greater  number  of  the  sensory  nerves  of  the  shin. 

The  2:>neumo-gastric  nerves  transmit  to  the  nervous  centre 
the  vague  sensory  impressions  made  upon  the  pulmonary 
surface,  which  impressions  constitute  the  desire  to  breathe. 
If  the  pneumo-gastric  nerve  be  cut  off  above  the  root  of  the 
lung,  and  its  central  extremity  excited,  the  respiratory  move- 
ments are  seen  to  become  more  forcible  and  rapid,  while  if 
the  excitation  be  very  great,  the  contraction  of  the  diaphragm 
is  changed  into  actual  tetanus,  so  that  animals  die  by  arrest 
of  tlie  respiration  while  in  a  state  of  tetanic  inspiration. 
One  of  the  fibres  of  the  pneumo-gastric  nerve  appears 
to  have  a  special  influence  over  the  respiratory  reflex  act:^ 
this  is  the  upper  laryngeal,  which  appears  especially  to  give 
rise,  in  opposition  to  the  pneumo-gastric  trunk,  to  phenomena 
of  expiration :  if  this  nerve  be  cut,  and  its  upper  (central) 
extremity  excited,  expiration  takes  place  with  great  force,  and 
if  tlie  excitation  be  very  forcible,  the  animal  falls  into  a  state 
of  tetanus  of  the  expiratory  muscles.  A  similar  phenomenon 
takes  place  in  the  complaint  known  as  whooping-cough, 
which  is  only  an  affection  of  the  superior  laryngeal  nerve  / 
inasmuch  as  it  excites  this  nerve,  and  increases  the  move- 
ments of  expiration  to  an  extraordinary  degree.  As,  during 
expiration,  the  diaphragm  is  passive,  so,  when  centripetal 

*  It  must  not,  however,  be  supposed  that  the  carbonic  acid  alone 
causes  respiration :  we  know  that  the  elements  of  the  nerve.!'*  cen- 
tres consume  oxygen,  just  as  do  the  other  elements  of  the  other 
tissues  when  at  work.  The  presence  of  a  large  quantity  of  car- 
bonic acid  in  the  blood  will  produce  no  respiratory  movement  if  the 
irritability  of  the  gray  matter  of  the  fourth  ventricle  has  ceased, 
on  account  of  the  want  of  oxygen,  as  in  cases  of  asphyxia. 

^  Spasm  of  the  diaphragm,  so  closely  associated  with  intestinal 
irritation  and  pleuritis,  may  be  caused  by  irritation  of  the  pneumo- 
gastric  nerve  conveyed  to  the  respiratory  centre.  I  have  observed 
that  administration  of  ipecacuanha  tends  to  the  increase  of  the 
spasm.     (Am.  ed.) 


REFLEX  RESPIRATION.  337 

excitation  of  the  upper  laryngeal  nerve  takes  place,  we  find 
it  entirely  relaxed  ;  and,  from  this  point  of  view,  the  superior 
laryngeal  nerve  may  therefore  be  considered  as  a  centripetal 
moderating  nerve  of  respiration. 

The  pneuino-gastric  nerve,  and  superior  laryngeal  branch, 
are  not,  however,  the  only  centripetal  respiratory  nerves ; 
respiration  does  not  cease  entirely  when  they  are  cut,  al- 
though it  changes  its  rhythmical  regularity.  There  are  other 
sensory  tracts  or  paths  which  bring  the  respiratory  centre 
into  action,  and  other  surfaces  than  the  pulmonary  surface 
which  serve  as  a  starting-point  to  these  centripetal  nerves. 
The  skin  and  its  nerves  perform  this  office.  It  is  impossible 
to  cut  all  the  nerves  of  the  skin  for  the  purpose  of  experi- 
menting on  these  latter  centripetal  conductors,  but  the 
cutaneous  surface  may  at  least  be  preserved  from  all  outward 
contact,  especially  from  that  of  the  air  or  of  water,  this  latter 
medium  appearing  equally  capable  with  the  air  of  affecting 
the  centripetal  nerves  of  respiration.  If  the  skin  be  covered 
with  an  impermeable  coating,  such  as  varnish,  the  respiration 
is  observed  to  become  more  feeble  and  slower,  ceasing  en- 
tirely in  some  cases,  and  in  all  becoming  insufficient :  as  a 
sufficient  quantity  of  oxygen  is  not  supplied,  combustion  is 
impeded,  the  animal  grows  cold,  and  dies ;  this  method  is 
frequently  employed,  in  physiological  laboratories,  for  the 
purpose  of  changing  a  warm-blooded  into  a  cold-blooded 
animal  by  a  slow  and  gradual  process  of  chilling.  Some 
eases  of  accident  have  shown  that  the  same  thing  takes  place 
in  man,  when  nearly  the  entire  skin,  or  a  great  part  of  it,  is 
destroyed.  In  the  large  breweries  in  our  towns  it  happens 
but  too  often  that  a  workman  falls  into  one  of  the  immense 
boilers  found  in  these  establishments ;  even  if  taken  out  im- 
mediately his  skin  will  be  found  scorched,  and  the  burns, 
though  sometimes  not  severe,  will  be  always  of  great  extent, 
and  seriously  modify  the  skin,  in  its  nervous  relations ;  as  is 
always  the  case  in  regard  to  the  sensibility  of  any  surface  of 
which  the  epithelium  is  injured.  In  some  cases  of  this  kind 
we  have  observed  that  the  influence  of  the  loill  is  necessary 
to  the  performance  of  respiration  with  the  usual  fulness  and 
intensity.  The  patient  then  breathes  because  he  desires  to 
breathe,  and  as  the  physiological  reflex  action  is  insufficient 
for  the  purpose  on  account  of  the  injury  to  the  centripetal 
organs,  the  movements  of  the  thorax  no  longer  exhibit  their 
accustomed  regularity  or  apparent  spontaneity;  if,  however, 
the  patient  forgets  to  breathe^  the  movements  of  the  thorax 

22 


338  PULMONARY  MUCOUS  TISSUE, 

become  slow  and  feeble,  as  in  the  case  of  an  animal  whose 
skin  is  covered  with  varnish ;  the  temperature  of  the  body  is 
lowered,  and  is  only  kept  up  by  the  influence  of  the  will  upon 
respiration.  Here  it  is  plain  that  one  of  the  sources,  the 
cutaneous  source^  if  we  may  so  speak,  of  the  respiratory  reflex 
system  has  been  withdrawn,  and  that  the  influence  of  the 
pneumo-gastric  nerve  alone  is  not  sufficient  to  excite  the 
action  of  the  central  nervous  system.  The  will  supplies  this 
lack  of  external  influence,  until  the  unfortunate  patient  con- 
demned to  this  extraordinary  species  of  suffering,  at  length 
yields  to  his  fatigue,  and  falls  asleep.  Respiration  then  be- 
comes so  feeble  that  the  temperature  of  the  body  is  consider- 
ably lowered,  and  death  finally  ensues.^ 

The  function  of  the  skin,  in  regard  to  respiration,  is  also 
demonstrated  by  a  number  of  medical  practices,  which  are 
very  common,  and  consist  in  exciting  the  respiratory  move- 
ments by  means  of  irritants  applied  to  the  skin:  such  as  fric- 
tion, eff'usions  of  cold  water,  cauterization,  and  the  more  for- 
cible methods  sometimes  employed  to  restore  life  in  persons 
apparently  drowned,  as  well  as  those  employed  to  excite,  in 
a  new-born  infant,  the  first  movement  of  inspiration,  which  is 
sometimes  delayed  and  performed  with  difficulty. 

3.  Centrifugal  l^aths. — It  is  scarcely  necessary  to  mention 
the  centrifugal  path  of  the  respiratory  reflex  system  here: 
anatomy  sufficiently  proves  that  this  is  along  motor  nerves 
which  leave  the  cervical  and  dorsal  parts  of  the  spinal  cord 
in  order  to  join  the  muscles  of  the  walls  of  the  thorax;  we 
will  only  mention,  as  being  the  most  remarkable,  the  joAremc 
nerve;  this  leaves  the  cervical  plexus^  and  innervates  the 
diaphragm ;  by  means  of  sections  of  the  spinal  cord  at  some 

^  As  the  pneumo-gastric  nerve  alone  is  powerless  to  excite  res- 
piration when  the  impressions  made  by  the  cutaneous  nerves  are 
withdrawn,  so  these  nerves  are  unable  of  themselves  to  keep  up  the 
reflex  action  when  the  pneumo-gastric  nerves  are  cut.  The  death 
of  animals  whose  vagi  nerves  have  been  divided  must,  no  doubt,  be 
ascribed  to  this  cause.  Physiologists  have  sought  to  discover  in 
the  stomach,  in  the  heart,  and  the  lungs  the  cause  why  death  so 
inevitably  follows  this  operation.  It  has  been  proved  by  numerous 
experiments  that  the  lungs  are  principally  affected;  since  animals 
whose  two  pneumo-gastric  nerves  have  been  cut,  have  been  fre- 
quently observed  to  die  in  a  few  days,  and  since  the  autopsy  showed 
that  the  lungs  were  not  impaired,  death  in  these  cases  should  be 
ascribed  to  the  suppression  of  the  sensory  or  centripetal  filaments 
of  the  pneumo-gastric  nerves.  (See  Paul  Bert,  "  Legons  sur  la 
Physiologie  comparee  de  la  Respiration,"  p.  496.) 


ANIMAL  HEAT.  339 

point  below  the  origin  of  this  nerve,  all  the  respiratory 
muscles  may  be  paralyzed;  the  diaphragm  is  thus  left  to 
work  alone,  and,  in  a  case  of  necessity,  it  is,  of  itself,  capable 
of  continuing  respiration. 


II.     ANIMAL  HEAT. 

Our  study  of  the  phenomena  of  the  lungs,  the  respiration 
of  the  tissues,  and  the  temperature  of  the  blood,  will  enable 
us  to  examine  rapidly  the  question  of  animal  heat,  a  question 
the  fundamental  data  of  which  we  are  already  familiar  with, 
and  which  requires,  for  its  completion,  only  a  few  special 
details. 

It  has  long  been  known  that  the  temperature  of  the  supe- 
rior animals  is,  up  to  a  certain  point,  independent  of  the  sur- 
rounding or  ambient  temperature :  these  animals  are  said  to 
have  a  constant  temperature ;  the  mammalia  and  birds  be- 
long to  this  class.  In  the  other  classes  of  the  animal  kingdom 
the  temperature  of  the  body  depends  more  or  less  on  the 
variations  in  the  external  temperature ;  and  the  animals  be- 
longing to  these  are  said  to  have  a  variable  temperature. 
The  former  have  also,  less  happily,  been  called  warni-blooded 
a7iimals,  and  the  latter  cold-blooded  animals} 

^  "  Between  the  physiological  properties  of  the  muscles  and 
nerves  of  the  warm-blooded  and  the  cold-blooded  animals  differences 
exist,  which  may,  perhaps,  be  owing  to  the  modifying  influence  of 
the  surrounding  or  ambient  medium.  Thus  the  muscles  and  nerves 
of  a  torpid  dormouse,  or  those  of  a  rabbit  under  certain  circum- 
stances (subjected  to  gradually  increasing  cold)  which  make  it 
resemble  a  cold-blooded  animal,  are  found  exactly  similar  to  those 
of  a  frog  or  a  tortoise  during  the  winter.  When  animals  are  in  a 
state  of  torpor,  the  nervous  excitation  spreads  slowly,  and  tlie  c<m- 
tractiou  of  the  muscles  lasts  after  the  excitation  of  the  nerve  has 
ceased,  while  in  those  which  are  not  benumbed  the  contraction  of 
the  muscles  takes  place  rapidly  at  the  moment  of  the  excitation, 
and  ceases  with  it.  The  special  modification  produced  by  cold  in 
the  muscles  and  nerves  of  animals  may,  however,  be  followed  by 
other  results:  In  the  warm-blooded  animals  the  nerves  and  muse  les 
belonging  to  the  system  of  the  great  sympathetic  nerve,  are  found 
endowed  with  the  same  properties  as  the  muscles  and  nerves  of  the 
cercbro-spinal  system  when  benumbed.  .  .  .  This  normal,  or  phy- 
siological, torpor  of  the  muscles  and  nerves  is  probably  due  to  a 
less  perfect  histological  organization,  accompanied  by  a  lower  de- 
gree of  excitability  or  irritability  of  the  organized  matter."     ((Jl. 


840  PULMONARY  MUCOUS  TISSUE. 

The  temperature  of  man  is  constant :  a  thermometer,  placed 
in  the  axilla  (arn^pit),  shows  it  to  be  always  about  37^  (C.)  ; 
if  we  examine  the  deeper  tissues  the  temperature  is  found  to 
increase  slightly,  while  in  the  extremities,  which  are  more 
exposed,  it  is  somewhat  lower. 

In  order  to  keep  up  the  temperature  of  the  body  and  resist 
the  effects  of  the  surrounding  atmosphere,  the  organism,  on 
the  one  hand,  produces  heat,  and  on  the  other,  possesses 
powerful  means  of  eliminating  any  excess  of  heat. 

It  is  now  proved  beyond  all  doubt  that  the  combustion 
which  takes  place  in  the  organism  is  the  source  of  animal 
heat :  by  means  of  the  oxygen  furnished  by  respiration,  we 
consume  the  carbon  and  hydrogen  of  the  food  received,  or 
of  our  own  tissues  (inanition).  It  is  well  known  that  the 
calorific  capacity  of  carbon  is  8000  units  of  heat,  and  th^t  of 
hydrogen  34,000 ;  in  other  words,  in  passing  into  the  state 
of  carbonic  acid  or  of  water,  1  kilog.  of  the  former  produces 
a  quantity  of  heat  capable  of  raising  80  kilogrammes  of  water 
from  0°  (C.)  to  100°  (C),  while  1  kilog.  of  the  latter  will 
raise  340  kilogrammes. 

Man,  on  an  average,  develops  daily  a  quantity  of  heat  esti- 
mated at  3250  units. 

Thus,  it  is  seen  that  we  produce  a  considerable  quantity  of 
heat  in  24  hours,  and  that  this  quantity  increases  with  in- 
creased activity  of  nutrition,  or  when  the  food  is  more  abun- 
dant and  rich  in  carbon  and  hydrogen;  the  food  of  the 
inhabitants  of  cold  countries  ought,  for  this  reason,  to  be 
richer  than  that  of  the  inhabitants  of  the  tropical  regions,  and 
to  contain,  especially,  a  larger  proportion  of  hydro-carbons, 
without  much  oxygen,  such  as  the  fats  which  the  Laplanders 
consume  in  such  quantities. 

The  heat  thus  produced  serves  to  keep  the  body  at  a  tem- 
perature of  37*^  (C),  and  to  raise  the  fluids,  etc.,  received,  to 
the  same  temperature.  By  the  aid  of  a  little  calculation, 
joined  to  what  we  know  of  the  subject  by  experiment,  we  are 

Bernard,  "  De  la  Physiologie  Ge'nerale.'*  1872,  p.  249.)  Legros 
observed  in  the  dormouse,  during  hibernation,  phenomena  which 
show  still  more  clearly  the  close  resemblance  between  the  cold- 
blooded and  the  hibernating  animals.  Phenomena  of  redintegra- 
tion take  place  in  the  latter  which  never  occur  during  their  waking 
hours.  For  instance,  if  the  tail  of  the  animal  in  this  state  be  cut 
off,  it  will  grow  again.  (See  P.  Bert,  Recherches  Experimentales 
pour  servir  a  I'Histoire  de  la  Vitalite  propre  des  Tissus  Animaux.'* 
18G0.) 


■ 


ANIMAL  HEAT.  341 

enabled  to  prove  satisfactorily  that  the  heat  produced  by  the 
combustion  of  the  hydrogen  and  carbon  of  the  food  is  suffi- 
cient .  to  account  for  all  the  animal  heat ;  where  this  heat 
varies,  it  is  always  found  that  some  excess  or  deficit  of  com- 
bustible material  has  occurred  in  the  animal  economy. 

As  to  the  exact  region  in  which  these  combustions  take 
place,  we  have  seen,  in  reference  to  respiration,  that  their 
seat  is  not  in  the  lungs,  but  in  the  capillaries,  in  the  very 
depth  of  the  tissues.^  We  know,  besides,  that  the  venous 
blood  is  generally  the  warmest ;  the  contact  with  the  air  in 
the  lungs  which  renders  it  arterial  chills  it  slightly.  The 
greater  the  combustion  in  an  organ,  the  warmer*  will  bo 
the  blood  that  flows  from  it;  as,  for  instance,  the  blood  of  the 
hepatic  veins  and  the  venous  blood  of  a  muscle  when  con- 
tracted. All  physiologists  are  now  agreed  as  to  the  complex 
nature  of  the  phenomena  producing  animal  heat.  The  only 
point  upon  which  they  differ  in  regard  to  it  is  the  relative 
importance  of  the  reactions  which  take  place  in  the  blood, 
and  those  which  have  their  seat  in  the  tissues.  Pasteur, 
Blondeau,  and  Camille  Saint-Pierre  give  the  supremacy  to 
the  former.^  Bernard  recognizes,  almost  exclusively,  not 
only  the  importance,  but  the  existence,  of  the  latter.  He 
maintains  that  heat  is  engendered  in  the  deepest  part  of  the 
organs,  in  close  contact  with  the  histological  elements,  by 
means  of  the  chemical  reactions  by  which  their  nutrition 

1  A  recent  observation  by  M.  Laboulb^ne  seems,  at  first  sight, 
worthy  of  notice,  in  reference  to  the  dispute  regarding  the  seat  of 
respiratory  combustion.  Being  desirous  of  ascertaining,  in  cases 
of  thoracentesis,  the  effect  to  be  produced  by  taking  away  the  fluid 
which  overflows  into  the  pleural  cavity,  M.  Laboulbene  performed 
this  operation,  and  found  that  the  temperature  invariably  rises  after 
it.  This  rise  is  explained  by  the  changes  produced  in  the  state  of  the 
respiratory  organs  by  the  withdrawal  of  the  fluid.  After  the  opera- 
tion the  lung  resumes  its  functions,  in  the  discharge  of  which  it  had 
been  hindered  by  the  compression  produced  by  the  overflow  of  the 
fluid:  the  air  again  freely  penetrates  the  pulmonary  vesicles,  as  is 
shown  by  the  disappearance  of  the  dulness,  and  the  presence  of  the 
respiratory  murmur  by  means  of  auscultation.  This  increase  of  pul- 
monary activity,  however,  does  not  immediately  precede  the  rise  in 
the  temperature.  The  entrance  into  the  lung  of  a  larger  quantity 
of  air  imparts  to  the  blood  (the  red  globules)  a  greater  proportion  of 
oxygen,  and  thus  enables  them  to  excite  the  inward  processes  of 
nutrition  and  combustion  which  take  place  in  the  tissues. 

^  See  "  Moniteur  Scientifique,"  du  Dr.  Quesneville.  Aout  et 
novembre,  1872. 


842  PULMONARY  MUCOUS  TISSUE, 

and  functions  are  accompanied.  These  reactions  are  ex- 
tremely complex;  consisting  of  separations,  fermentations, 
etc. 

The  attempt  has,  however,  been  made  to  determine  more 
exactly  the  seat  of  these  combustions ;  are  they  produced  in 
the  histological  elements  themselves,  or  in  the  capillary 
vessels  which  come  in  contact  with  these  elements  ?  The 
German  physiologists,  who  have  made  a  special  study  of  this 
question,  are  divided,  in  regard  to  it,  into  two  schools.  1. 
Ludwig  and  his  followers  maintain  that  the  act  of  oxidation 
and  the  production  of  carbonic  acid  take  place  in  the  interior 
of  the  capillary  vessels.  The  arguments  adduced  in  favor  of 
this  opinion  rest  chiefly  on  the  recent  analyses  made  by  Ham- 
marsten  of  the  gases  of  the  lymph  :  these  show  that  this  fluid 
which  carries  off  the  disintegrated  parts  of  the  tissues,  directly 
contains  a  smaller  quantity  of  carbonic  acid  than  the  venous 
blood ;  whence  they  conclude  that  the  carbonic  acid  is  not 
produced  in  the  histological  elements.  2.  Pfliiger  corisiders 
that  the  tension  of  the  carbonic  acid  in  the  lymph  does  not 
give  the  exact  measure  of  the  tension  of  this  gas  in  the  histo- 
logical elements  themselves.  In  order  to  estimate  this  ten- 
sion as  directly  as  possible,  Pfluger  has  recourse  to  the  normal 
secretions  of  the  economy  (the  urine,  bile,  saliva),  which, 
being  the  immediate  result  of  the  destruction  of  the  cellular 
elements,  must  represent  exactly  the  amount  of  carbonic  acid 
which  these  contain.  In  all  these  secretory  products  the 
tension  of  the  carbonic  acid  is  much  greater  than  in  the 
venous  blood.  Pfluger  concludes  from  this,  that  carbonic 
acid  is  formed  in  the  tissues,  and  not  in  the  blood,  and  that 
the  seat  of  the  respiratory  combustions  is  to  be  found  in  the 
deeper  tissues. 

The  heat  thus  produced  in  all  the  different  parts  of  the 
organism,  and  more  especially  in  some  internal  foci  (the 
liver)  is  equally  distributed  throughout  the  body  by  the  cir- 
culation of  the  blood ;  the  more  vascular  any  part  of  the 
body  is,  the  more  active  is  the  circulation  in  it,  and  the  more 
nearly  it  approaches  the  maximum  of  its  temperature :  in 
some  parts  (the  choroid  plexus,  articulations,  etc.)  the  vascu- 
lar richness  serves  no  other  purpose  than  that  of  warming  the 
part  (see  Circulation  and  Vaso-motors). 

A  loss  of  heat  from  the  surface  of  the  body  takes  place 
when  the  environment  is  of  lower  temperature  than  that 
of  our  bodies;  the  organism,  however,  possesses  various 
methods  of  mitigating  the  injurious  effects  produced  by  this 


ANIMAL  HEAT.  343 

radiation.  The  entire  body  is  covered  by  a  corneous  envelope 
formed  by  the  supei-ficial  layers  of  the  epidermis.  The  greater 
part  of  the  body  is,  moreover,  covered  with  down  or  hair,  en- 
closing a  layer  of  air,  which  forms  a  covering  as  little  adapted 
to  be  a  conductor  of  heat  as  the  layers  of  the  epidermis. 
Finally,  a  special  layer  of  areolar  tissue  is  found  in  the 
dermis  (sec  for  all  these  parts.  Physiology  of  the  external 
Integ^iment)^  called  the  subcutaneous  tissue,  or  adipose 
pannicle,  formed  of.  cells  filled  with  fat,  and  affording  a  pro- 
tecting envelope  as  regards  heat,  and  appearing  most  highly 
developed  in  cases  in  which  the  loss  of  heat  appears  most 
probable  (as  in  that  of  newly  born  animals  and  animals  of  the 
polar  regions).  We  also  possess  numerous  and  important 
blood  currents,  circulating  with  much  greater  activity  than  is 
required  for  the  purpose  of  nutrition,  in  tlie  parts  more  par- 
ticularly exposed  to  cold,  such  as  the  pinna  of  the  ear,  the 
face  (especially  the  nose),  the  hands,  and  the  extremity  of 
the  fingers;  these  currents  considerably  increase  the  heat  of 
these  parts  of  the  body. 

The  organism  has  more  difficulty  in  withstanding  a  too 
great  rise  in  the  external  temperature.  For  this  purpose  we 
find  that  organs  are  employed  which  we  have  mentioned  as 
being  endued  with  very  slight  conducting  power,  such  as  the 
cells  of  the  epidermis,  the  air  enclosed  in  the  pilous  covering 
or  hair,  and  the  adipose  panicle.  The  most  effectual  means, 
however,  of  resisting  too  great  an  elevation  of  temperature 
are  found  in  the  phenomena  of  evaporation  which  take  place 
in  the  lungs  and  on  the  surface  of  the  skin. 

With  regard  to  the  lungs,  we  know  that,  in  general,  while 
the  10  cubic  metres  of  air  inhaled  in  24  hours  contain  only 
from  50  to  60  grms.  of  vapor,  the  air  exhaled  contains,  on  an 
average,  from  300  to  400  grms.,  and  often  more :  we  find,  by 
calculation,  that  from  200  to  300  heat-units  are  probably  em- 
ployed in  turning  this  water  into  vapor  at  35^*  or  36®  (C.) 
(the  temperature  of  the  exhaled  air)  ;  this  loss  of  heat  may- 
be carried  to  a  much  higher  point ;  for  instance,  in  animals 
which,  like  the  dog,  scarcely  perspire  at  all,  except  through 
the  lungs,  it  forms  the  principal  means  of  equilibrium  of  the 
internal  heat,  when  this  is  increased  to  too  great  a  degree,  as 
in  violent  exercise,  running,  etc. 

The  evaporation  of  sweat,  from  the  surface  of  the  skin,  is 
the  principal  means  possessed  by  man  of  withstanding  an 
excess  of  heat.  We  shall  consider  this  subject  at  greater 
length  when  studying  the  functions  of  the  skin,  especially  the 


1 


844  PULMONARY  MUCOUS  TISSUE. 

Becretion  of  the  sudoriferous  glands  ;  we  need  only  mention 
in  this  place  that  the  function  of  the  exhalation  from  the  skin, 
alone  explains  why  dry  heat  is  more  easily  supported  than 
moist :  evaporation  is  almost  powerless  against  the  latter,  the 
ambient  medium  being  already  almost  saturated  with  vapor ; 
on  the  other  hand,  sui-prising  instances  have  been  known  of 
extreme  external  heat  being  neutralized  by  violent  sudation, 
and  considerable  evaporation  of  sweat :  thus,  instances  have 
been  known  of  persons  who  have  supported  for  ten  minutes 
and  more  a  temperature  of  130  degrees  (C).  In  such  cases 
the  secretion  of  the  sweat  becomes  a  hundredfold  greater 
than  in  the  normal  state,  and,  consequently,  causes  a  great 
loss  of  heat :  the  latent  heat  of  the  vaporization  of  water  is 
equal,  as  we  know,  to  540. 

Man's  temperature,  at  every  stage  of  his  life,  is  connected 
with  the  combustion  which  takes  place  in  the  tissues.  The 
temperature  of  an  infant,  just  born,  is  nearly  the  same  as  our 
normal  temperature;  it  is  only  a  little  lower;  a  child  of  this 
age  is,  however,  very  susceptible  to  outward  changes  in  the 
atmosphere,  and  is  rarely  capable  of  maintaining  the  tempera- 
ture natural  to  it.  Some  general  laws  have  been  deduced  from 
experiments  made  on  this  subject.  The  temperature  of  those 
animals,  mammals  or  birds,  which  are  born  with  the  eyes 
open,  or  with  down  upon  their  bodies,  remains  always  the 
same  as  at  birth,  provided  there  are  no  very  decided  causes 
of  loss  (this  being  the  case  particularly  in  regard  to  man) ; 
on  the  other  hand,  birds  hatched  without  feathers,  mam- 
mals born  with  the  eyes  open,  and  children  born  prema- 
turely, are  unable  to  maintain  this  temperature.  Thus  a 
rabbit  cannot  maintain  that  temperature,  35  or  36  deg.  (C), 
which  it  had  at  birth:  the  want  of  activity  of  combustion  is 
the  cause  of  all  young  animals  offering  so  little  resistance  to 
cold,  while  it  is  also  the  cause  of  their  being  able  to  resist 
suffocation ;  their  respiration  being  less  active  than  that  of 
adults,  the  want  of  oxygen  has  less  effect  upon  them  than 
upon  persons  who  require  a  large  quantity  for  consumption 
(adults,  see  p.  334) .^ 

As  respiration  grows  more  active  in  man,  so  the  heat  pro- 
duced increases,  and  the  child,  a  few  months  after  birth,  is 
enabled  to  support  cold  in  a  remarkable  manner.  Later,  the 
respiration  of  a  young  person  is  superior  to  that  of  the  adult; 

1  *See  Gavarret,  "  De  la  Chaleur  produite  par  les  Etres  Vivants. " 
Paris,  1855. 


ANIMAL  HEAT.  345 

the  latter  consuming  in  the  proportion  of  100,  and  the  former 
150. 

At  the  stage  where  growth  ceases,  however,  a  diminution 
is  observed  in  the  production  of  carbonic  acid  and  the  quan- 
tity of  animal  heat ;  not  that  the  temperature  is  sensibly 
lowered,  for  the  greater  the  size  of  a  body,  the  less  is  the  loss 
that  takes  place  by  radiation ;  the  cold  produced  by  radiation 
affects  an  animal  in  proportion  to  its  size,  the  surfaces  by  which 
loss  occurs  varying  in  individuals  of  the  same  kind  only  by 
squares,  while  the  bulk  varies  by  cubes;  consequently  an 
adult  who  weighs  eight  times  more  than  a  child,  has  a  surface 
only  four  times  as  large,  and  loses,  proportionately,  only  half 
as  mucli  heat  by  radiation  (2.  —  4.  —  8.)  This  explains  the 
fact  that  the  smaller  animals  produce  more  heat  (in  propor- 
tion to  their  weight  and  bulk)  than  the  larger  animals;  the 
fact  being  that  they  lose  more  by  radiation  and  contact,  on 
account  of  their  surface  being  larger  (in  proportion  to  their 
bulk). 

Aged  persons  have  less  animal  heat  than  adults,  the  phe- 
nomena of  nutrition  and  combustion  being  diminished  in  their 
case.  There  is  always  a  connection  between  the  consumption 
of  oxygen  and  the  production  of  carbonic  acid  and  of  heat 
(see  again.  Physiology  of  the  Muscle). 

Numerous  instances  of  these  facts  appear  in  pathology.  In 
cholera,  for  instance,  in  which  respiration  ceases  to  be  a  func- 
tion, properly  so-called,  and  appears  to  be  reduced  by  the 
state  of  tlie  blood  to  the  entrance  and  exit  of  the  air,  the  body 
becomes  perfectly  cold.  In  febrile  affections  there  is  an  in- 
crease of  caloric,  which,  we  know,  is  followed  by  great 
activity  in  the  circulation  and  respiration,  and  in  the  com- 
bustion which  takes  place  in  the  tissues. 

The  nervous  system  has  plainly  some  influence  upon  the 
production  of  animal  heat,  but  this  influence  is  very  compli- 
cated, and,  in  some  respects,  difficult  to  explain.  The  heat 
produced  by  the  organs  (muscles,  glands,  and  nervous 
centres),  being  in  direct  proportion  to  the  activity  of  their 
functions  (that  is  of  the  oxidation  produced  in  them),  it  is 
plain  that  the  nerves,  by  means  of  which  they  perform  their 
functions,  increase  the  heat  by  that  very  fact;  thus  Ilaller 
observed,  long  since,  that  a  paralyzed  limb  is  usually  colder 
than  when  in  health.  Some  physiologists  have,  unfortunately, 
mistaken  the  nature  of  this.inliuence  of  the  nervous  system ; 
thus  Brodie  and  Chossat,  having  removed  the  cncephalon 
and  cut  the  spinal  cord  of  animals  whose  respiration  they 


346  PULMONARY  MUCOUS  TISSUE. 

artificinlly  kept  up  (a  process  which  induces  cooling,  if  too 
energetic.'illy  performed),  observed  that  the  temperature  was 
considerably  lowered,  and  thence  formed  the  opinion  that 
calorification  is  due  to  a  more  or  less  mysteiious  influence  of 
the  nervous  system.  It  has  been  since  discovered  that  the 
cerebro-spinal  nervous  system  modifies  the  production  of 
animal  heat  by  acting  on  the  tissues  and  giving  rise  to  the 
chemical  processes  of  oxidation  and  separation  which  accom- 
pany their  vital  manifestations. 

The  effect  produced  by  the  great  sympathetic  nerve  on 
calorification  is  not,  however,  yet  fully  decided.  We  know 
that  if  this  nerve  be  divided  or  paralyzed,  hyperaemia  of  the 
corresponding  parts  of  the  body  follows,  and  is  accompanied 
by  a  rise  in  the  temperature.  On  the  other  hand,  galvanization 
of  the  peripheral  extremity  of  the  great  sympathetic  nerve 
causes  anaemia  of  the  coiTesponding  parts,  accompanied  by  a 
fall  in  the  temperature  (see  p.  170).  Are  these  changes  of 
temperature  simply  due  to  a  more  or  less  considerable  afflux 
of  blood,  which  forms  the  vehicle  of  the  heat  produced  in  the 
principal  internal  seats  of  combustion  (the  liver,  the  spleen,  and 
the  viscera  in  general),  or  does  the  great  sympathetic  nerve  pro- 
duce any  immediate  effect  upon  calorification,  beyond  the 
influence  exercised  by  its  vaso-motor  network?  This  is  a 
much  disputed  question,  and  very  difficult  to  answer.  Claude 
Bernard  first  directed  attention  to  the  subject  of  the  great 
sympathetic  nerve,  and  its  influence  on  the  circulation  and  on 
the  temperature  of  the  parts  through  which  it  passes;  and  he  has 
hitely  resumed  the  investigations  which  have  already  yielded 
such  abundant  fruits,  seeking  especially  to  determine  the  calor- 
ific function  of  this  nerve(course  of  1872).^  This  question  brings 
us  back  to  the  much  controverted  subject  of  the  trophic 
nerves .  "  Some  physiologists  have  supposed  that  there  exists 
a  third  class  of  nerves  (beside  the  sensory  and  the  motor), 
called  trophic  nerves  ^  that  these  immediately  govern  the 
phenomena  of  interior  nutrition,  and  regulate  the  exchanges 
which  occur  in  the  deep  tissues,  and  which  constitute  the 
assimilation  and  dis-assimilation  (constructive  and  destructive 
metamorphoses)  of  the  elements.  Their  existence  has  never 
been  demonstrated  by  anatomy,  and  physiology  and  patho- 
logy have  not  yet  sufficiently  proved  their  necessity"  (CI. 
Bernard).  Claude  Bernard,  however,  seems,  after  all,  to 
attribute  to  the  great  sympathetic  nerve  some  office  of  this 

*  **  Revue  des  Cours  Scientifiques. "    Mai  et  juin,  1872. 


LARYNX  AND  PHO NATION. 


347 


kind.  "  We  believe  that  the  great  sympathetic  system  is  not 
simply  a  vaso-motor  nerve;  it  has  a  direct  influence  on 
calorification,  its  essential  office  being  the  regulation  of  the 
chemico-physical  phenomena  whiqh  take  place  in  the  tissues, 
when  these  enter  into  conflict  with  the  blood  by  means  of 
the  capillary  circulation."  He  holds  that  this  nerve  acts  as 
a  constant  check  upon  the  circulation,  and  also  serves  to 
modify  the  oxidation  that  goes  on  in  the  tissues  as  well  as  the 
decompositions  which  produce  heat ;  producing,  after  section 
of  the  sympathetic,  an  increase  of  vascularization  and  calori- 
fication, both  of  which  phenomena  are  entirely  local. 


III.  OF  THE  LARYNX  AND  PRONATION. 


As  we  shall  presently  find  that  the  external  integuments 
are  modified  in  certain  parts,  for  the  purpose  of  more  readily 
receiving  the  impressions  made  by  the  external  world,  thus 
constituting  the  organs  of  the  senses,  so  we  shall  find  that  the 
air-bearing  respiratory  tube  exhibits  in  the  upper  part  of  the 
neck  a  special  arrangement,  constituting  the  larynx,  an  organ 
which  places  man  in  relation  with  the  outer  world,  and 
especially  with  his  kind.  This  organ  is  one  of  the  most 
important  of  those  which  serve  the  purposes 
of  animal  life  (fonctions  de  relation),  form- 
ing, as  it  does,  our  principal  means  of  com- 
munication, in  fact,  of  expression. 

The  other  organs  of  commimication  and 
expression  are  scattered  throughout  the 
various  external  organs:  thus  the  limbs,  es- 
pecially the  arms,  are  organs  for  expression, 
the  signs  of  which  are  generally  easily  under- 
stood. The  muscular  system  of  the  face 
forms  a  special  organ  of  expression ;  all 
these  muscles,  with  the  exception  of  those  of 
the  globe  of  the  eye,  are  innervated  by  the 
facial  nerve  of  the  seventh  pair,  which  is 
Tinder  the  control  of  the  medulla  oblongata  / 
thus  the  thousand  varieties  of  expression 
presented  by  the  face  may  be  produced  by  a  simple  reflex 
action,  without  any  participation  of  the  will. 

*  The  lanmgeal  part  of  the  air-passa^^e  presents  three  circumsciibed  aper- 
tures or  embrasures:  1,  in  the  aryteno-epmlottidean  folds  ;  2,  in  the  imper  vocal 
cords ;  3,  in  the  lower  vocal  cords.    V,  V,  Ventricles  of  the  larynx.    T,  Trachoa- 


Fig.  84.  —  Diagram 
of  vertical  section 
of  the  larynx.* 


848 


PULMONARY  MUCOUS  TISSUE. 


Larynx.  —  The  larynx,  which  is  the  essential  organ  of 
phonation,  is  only  a  portion  of  the  trachea^  modified  in  its 
form,  and  in  some  degree,  in  its  structure.  In  regard  to 
form.,  the  trachea  exhibits,  in  this  part,  a  contraction,  or  kind 
of  strait.,  the  dimensions  of  which  may  be  diminished,  or  in- 
creased to  such  a  degree  as  to  bring  the  trachea  almost  to  its 
original  calibre.  This  narrowed  passage,  or  laryngeal  strait, 
is  multiple,  as  shown  in  the  dingram  (Fig.  84)  of  the  vertical 
section  of  the  larynx.      There  are  three  constrictions,  the 

first  of  which  is  circumscribed 
(from  top  to  bottom) ;  by  the 
aryteno-epiglottidean  folds,  the 
second,  by  the  false  or  superior 
vocal  cords  (which  are  simply  a 
fold  of  the  mucous),  and  the  third, 
by  the  true  vocal  cords  ^'  the  latter 
alone  forms  the  veritable  glottis, 
or  phonating  aperture.  In  regard 
to  structure.,  we  find  the  same  ele- 
ments in  the  glottis  as  in  the 
trachea,  being  modified  in  both  to 
answer  a  special  purpose.  Thus, 
while  the  epithelium,  throughout 
the  whole  extent  of  the  respiratory 
tree,  is  columnar  and  vibratile, 
that  which  is  found  at  the  spur 
formed  by  the  glottis  properly  so- 
called,  assumes  the  pavement  form, 
which  is  better  suited  to  the  func- 
tions of  the  vocal  cords.  This 
epithelial  coat  consists  of  more 
numerous  layers  than  the  vibratile 
epithelium,  and  is  also  better  fitted 
Fig.  85. -Intrinsic  muscles  of  the  to  prevent  the  dryinsf  of  the  eda:e8 

larynx,  seen  from  the  side.*  ^*  .,,         ,  "^i^i.,!        * 

01  an  orifice  through  which  the  cur- 
rent of  air  passes  with  so  great  force.     Below  the  mucous  we 


(.i^tiii' 


>X<»«^'' 


*  The  left  ala  or  wing  of  the  thyroid  cartilage  (0  is  disarticulated  and  cut 
rear  its  projecting  angle,  e,  Epiglottis,  cr,  Cricoid.  /,  Thyroid  articulating 
surface,  ar,  Arytenoid  cartilage,  tr,  Transverse  arytenoid  muscle,  o,  Oblique 
arytenoid  muscle,  p,  Posterior  crico-arytenoid  nmsclo.  /,  Lateral  crico-aryten- 
oid  muscle,  i,  Inferior  layer,  and  S,  superior  layer,  of  the  thyro-arytenoid 
muscle  C(ir^  cfa,  and  cte,  Muscular  fibres  which  are  not  constant,  but  extremely 
variable,  and  are  contained  in  the  aryteno-epiglottidean  folds,  being  known  by 
the  name  of  thyro-epiglottidean  muscles.  (L.  Mandlj  "  Traits  des  Maladies  d*u 
Larynx.) 


LARYNX  AND  PHONATION.  349 

find  the  clastic  tissue  which  we  have  already  observed  along 
the  trachea,  formed,  as  always,  of  fibres  irregularly  inter- 
laced and  twisted  like  horse-hair  in  a  mattress ;  at  the  glottis 
this  tissue  forms  a  thicker  layei-,  which  has  been  considered 
in  anatomy  as  a  ligament,  subjacent  to  the  mucous  layer;  this 
is  what  is  called  the  vocal  cord. 

Below  this  elastic  tissue  is  also  found  the  muscular  layer, 
as  is  the  case  throughout  the  respiratory  tree ;  in  the  larynx, 
however,  we  find  the  striated  and  not  the  smooth  musile: 
it  forms  here,  as  in  all  the  organs  of  animal  life  (vie  de 
relation),  clearly  defined  muscular  bodies,  and  with  functions 
well  determined  (posterior  crico-arytenoid  muscles,  lateral 
crico-arytenoid  muscles,  ary-arytenoid,  and  thyro-arytenoid 
muscles),  (Fig.  85).  Finally,  the  cartilaginous  rings  of  the 
trachea  are  also  arranged  for  the  purpose  of  forming  special 
and  characteristic  pieces  or  parts  (thyroid,  cricoid,  and  ary- 
tenoid cartilages),  (Figs.  87  and  88). 

Aperture  of  the  Glottis. — The  inferior  laryngeal  constric- 
tion, or  glottis,  properly  so-called,  exhibits,  when  examined 
from  above,  the  form  of  a  triangular  slit,  like  the  head  of  a 
spear,  the  upper  part  being  in 
front,  and  the  base  behind :  this 
base  is  formed  by  the  ary-aryte- 
noid muscles.  The  sides  of  the 
triangle  are  composed  in  its  an- 
terior three-fifths  by  the  vocal 
cords,  in  the  posterior  two-fifths 
bv  the  edges  of  the  arytenoid 
cartilages  (Figs.  86,  87,  88,  89, 

90).      These  cartilages   form  tri-    Fig.  86. -Aperture  of  the  glottis,  seen 

anovular  ]»yramids :  tlieir  base  is      \^  the  living  body  by  means  of  the 

r  •         1  £•   J.^  1  x-       laryngoscope.* 

a  triangle,  one  oi   the  angles  oi 

which  is  anterior,  another  posterior,  and  the  third  external ; 
one  of  the  sides  of  this  triangle  is  thus  internal,  and  forms 
the  posterior  part  of  the  glottis.  Each  arytenoid  cartilage, 
at  its  articulation  with  what  is  called  the  articidar  facet  of 
the  cricoid  (see  Figs.  87  and  88,  and  farther  on.  Figs.  90  and 
91),  can  turn  on  its  vertical  axis,  in  such  a  manner  that  its 
anterior  angle  (or  vocal  process)  is  turned  either  inwards 
I  or  outwards,  thus  necessarily  modifying  the  whole  form  of 
I       the  rima  glottidis  (or  glottid  chink),  since  this  angle  is  the 

r 


or.  Aperture  of  the  glottis,  ri,  Lower  vocal  cords,  rs,  Upper  vo(.al  cords 
flr,  Arytenoid  cartilage,  rap,  Aryteno-cpiglottidean  folds,  b,  Cuslxion  on  the 
epiglottis.    (L.  Maudl.) 


350  PULMONARY  MUCOUS  TISSUE. 

point  of  attachment  for  the  vocal  cord,  and  occupies  the  an- 
terior three-fifths. 


UMilUjtl    d>  ^  S^TUttt^t 


Fig.  87.  —  External  posterior  surface  of  the       Fig.  88.  —  Anterior  surface  of  the 
cricoid  and  arytenoid  cartilages.*  cricoids  and  the  arytenoids.f 

If  the  anterior  angle  of  the  arytenoid  cartilage  be  turned 
outwards,  the  glottis  will  be  dilated,  and  take  the  shape  of  a 
lozenge  or  rhomb  (Fig.  89).  This  effect  is  produced  by  the 
contraction  of  the  posterior  crico-arytenoid  muscle,  which  is 
inserted  in  the  external  angle  of  the  arytenoid  cartilage,  and 
produces  a  rocking  of  the  thyroid  upon  the  cricoid  cartilage 
{inouvetnent  de  sonnette). 

If  the  anterior  angle  of  the  arytenoid  cartilage  be  turned 
inwards,  the  anterior  portion  of  the  glottis  takes  the  form  of  a 
slit,  which  is  widened  posteriorly  into  a  small  inter-arytenoid 
triangular  aperture  (Fig.  90). 

Finally,  this  latter  opening  may  be  itself  reduced  to  a  slit 
by  a  second  movement  which  brings  the  two  arytenoids  close 
together  (Fig.  91).  The  first  action  is  produced  by  the 
lateral  crico-arytenoid  muscle,  which  causes  the  arytenoi<l 
cartilage  to  swing  in  a  contrary  direction  to  that  of  the 

^. 

*  rt,  Cricoid  cartilage,  h.  Its  median  projection,  c,  Articulating  thyroid 
surface,  rf,  Lower  edge,  e,  Upper  edge.  J,  Posterior  surface  of  the  arytenoid 
cartilages,  i,  Articulating  arytenoid  surface  of  the  crycoid  cartilage,  m,  Mus- 
cular process  (external  angle  of  the  base  of  the  arytenoid),  t?,  Vocal  process, 
contracted  (anterior  angle  of  the  base  of  the  arytenoid),  r,  Small  cornua. 
(L.  Mandl.) 

t  Cricoid  cartilage,  inner  surface.  6,  Section  of  the  surface  of  the  annular 
portion  after  removal.  (/,  Lower  edge,  e,  Upper  edge  of  the  cricoid,  m,  Mus- 
cular process  (external  angle),  v,  Vocal  process  (anterior  angle).  »•,  Small 
cornua.  i,/),  /,  ^,  ,  Protuberances  and  depressions  of  the  antero-external  surface 
of  the  arytenoid,  which  serve  as  points  of  insertion,  being  muscular  in  the  case 
of  the  most  external  fibres  of  tlie  thyro-arytenoid,  and  ligamentous  in  that  of 
the  upper  v  ical  cordis.    (L.  Mandl.) 


LARYNX  AND  PHONATION. 


351 


Fig.  89. — Lozenge  Bhitpe  of  the  glottis,  produced  by.  the  acfion  of  the  posterior 
crico-arytenoid  muscles.* 


Fig.  90.  —Occlusion  of  the  interligamentous  part  of  the  glottis.t 

•  Diagram  showing  a  horizontal  section  of  the  cartilages  of  the  larynx,  at 
the  level  of  the  base  of  the  arytenoid  cartilages.  The  dotted  lines  indicate  the 
new  position  of  the  cartilages,  caused  by  the  action  of  the  muscles  working  in 
the  direction  of  the  arrow.    (L.  Mandl,  '*  Traits  des  Maladies  du  Larjoix.") 

t  Action  of  the  lateral  crico-arytenoid  muscles,  acting  in  the  direction  indi- 
cated, by  the  arrows,  for  the  purpose  of  bringing  the  arj'tenoid  cartilages  and 
the  vocal  cords  into  the  position  indicated  by  the  dotted  Imes.    (L.  Mandi.) 


352 


PULMONARY  MUCOUS  TISSUE. 


posterior  crico-arytenoid ;  the  second  action  is  produced  by 
the  contraction  of  the  muscle  which  forms  the  base  of  the 
triangle  of  the  glottis,  the  ary-arytenoid  muscle,  which  dis- 
places all  the  arytenoid  cartilages,  and  makes  them  slide  in- 
wards (Fig.  91). 


Fig.  91.  —Entire  obliteration  of  the  aperture  of  the  glottis.* 

All  modifications  in  the  form  of  the  glottis  are  owing  to 
these  two  kinds  of  movement :  the  rocking  movement^  and 
movement  of  displacement  of  the  whole  box ;  the  two  ex- 
treme fjrms  of  the  glottis  thus  produced  are  the  lozenge 
shape,  which  appears  during  inspiration,  and  the  linear  form, 
to  which  a  tendency  is  shown  during  expiration  (see  Hespir- 
ation,  p.  302) :  this  is,  however,  more  especially  connected 
with  phonation  and  straining :  this  explains  Avhy  we  often 
hear  a  sound,  or  peculiar  cry,  uttered  by  a  person  who  is 
making  any  great  effort.  We  also  see  that  one  only  of  the 
four  intrinsic  or  interior  muscles  of  the  larynx  serves  to  dilute 
the  glottis :  this  is  the  posterior  crico-arytenoid ;  the  lateral 
crico-arytenoid  and  the  ary-arytenoid  serve  to  obliterate  it, 
and  reduce  it  to  the  condition  of  a  chink.  We  must  also 
observe  that  the  contraction  of  the  thyro-arytenoid  muscle, 
which  is  situated  in  the  thickest  part  of  the  glottis,  like  all 
curved   muscles   placed   around  an   aperture,  conij^letes  its 

*  Action  of  the  arytenoid  muscles,  median  movement  of  the  arytenoid  car- 
tilaj^es,  in  the  direction  indicated  by  the  two  arrows.  The  dotted  lines  indicate 
the  new  position  of  the  arytenoids  and  the  new  form  of  the  glottis.    (L.  Maudl.) 


LARYNX  AND  PEON  ATI  ON.  353 

closure ;  we  shall  discover,  however,  that  the  contraction  of 
this  muscle  has  to  fulfil  another  and  very  important  func- 
tion. 

We  have  not  mentioned  an  extrinsic  or  exterior  muscle  of 
the  larynx,  called  the  crico-thyroid.  The  influence  exerted 
by  it  over  the  glottis  is  unimportant :  it  causes  the  thyroid 
cartilage  to  rock  forwards,  rotating  it  forwards  and  down- 
wards on  the  cricoid  cartilage;  this  action,  although  it  elon- 
gates the  glottis  by  elongating  the  fibrous  parts  leading  from 
the  inner  surface  of  the  thyroid  to  the  anterior  apophysis  of 
the  arytenoid  cartilages,  has  not  this  effect  in  phonation,  a8 
direct  experiment  has  proved.  The  functions  of  this  muscle 
appear  to  be  connected  rather  with  deglutition  than  with 
phonation,  the  muscle  itself  being  innervated  by  the  same 
nerve  as  tlie  constrictor  muscle  of  the  pharynx  {superior  la- 
ryngeal nerve,  external  branch). 

Mechanism  of  Phonation.  —  Experiments  upon  animals, 
accidental  observation  in  the  case  of  man,  and  attempts  at 
artificial  phonation  made  with  detached  larynges,  all  prove 
that  the  sound  of  the  voice  is  produced  in  the  glottis.  In 
forming  this  sound,  we  know  that  the  glottis  contracts :  thus, 
it  was  at  first  supposed  that  the  vocal  organ,  in  its  inner 
mechanism,  resembled  a  whistle^  the  sound  being  produced 
by  the  vibration  of  the  air  in  passing  through  a  small  orifice, 
and  becoming  sharper  in  proportion  to  the  smallness  of  the 
orifice. 

It  is  now  proved  that  it  is  not  the  air,  but  the  edges  of 
the  glottis^  which  vibrate  in  this  organ ;  the  larynx,  therefore, 
rather  resembles  a  reed-pipe  than  a  whistle.  There  is, 
however,  another  analogous  organ,  which  also  acts  like  a 
reed ;  this  is  the  buccal  orifice^  the  lips,  which  vibrate  as  in 
playing  the  horn,  for  instance ;  it  is  needless  to  show  the 
anatomical  analogy  between  the  orifice  of  the  mouth  and  that 
of  the  glottis.^ 

In  order  to  vibrate,  however,  the  edges  of  the  glottis  must 
be  tense.  It  was  supposed  that  the  vocal  cords  adjoining  the 
mucous  were  stretched  by  the  contraction  of  certain  muscles. 
Miiller  made  the  experiment  of  causing  a  rapid  current  of  air 

*  "  There  is  no  authority  for  comparing  the  inferior  thyro- 
arytenoid fold  either  to  cords  or  ribbons:  it  is  much  better  to  call 
them  simply  inferior  folds,  or,  if  an  anatomical  name  be  desired, 
more  expressive  of  their  configuration  and  function,  the  vocal  lips.^* 
L.  Mandl,  "  Traite  Pratique  des  Maladies  du  Larynx  et  du 
haryux."     Paris,  1872.) 

23 


i 


854 


PULMONARY  MUCOUS  TISSUE. 


to  pass  through  a  larynx,  in  which  he  had  represented  the 
contraction  of  the  crico-thyroid  muscles,  by  the  traction  of  a 
weight  fastened  in  front  of  the  thyroid  cartilage ;  he  thus 
obtained  a  sound  by  the  vibration  of  the  vocal  cords,  stretched 
by  the  rocking  movement  of  the  thyroid  cartilage. 

Nothing,  however,  proves  that  this  is  the  case  in  phona- 
tion :  if  the  edges  of  the  glottis  were  stretched  in  this  man- 
ner, the  glottis  would  be  necessarily  elongated;  close  ex- 
amination, however,  shows  that  the  glottis  is  elongated 
scarcely  at  all  during  phonation,  and  since  the  tension  by  rock- 
ing of  the  thyroid  cartilage  is  produced  by  the  crico-thyroid 
muscle,  the  latter  would  then  play  the  chief  part  in  the 

process  of  phonation.  If  the 
nerve  leading  to  it  (the  exter- 
nal branch  of  the  upper  laryn- 
geal nerve)  be  cut,  its  paralysis 
has  hardly  any  effect  on  the 
voice,  while  section  of  the  in- 
ferior laryngeal  nerve  produces 
immediate  loss  of  phonation, 
although  this  nei-ve  leads  only 
to  the  intrinsic  muscles  of  the 
larynx,  and  not  to  the  crico- 
thyroid. 

It  is  plain  that  the  lips  of 
the  glottis  must  be  stretched, 
in  order  to  vibrate,  but  we 
do  not  yet  know  which  of  the 
tissues  composing  these  lips 
is  susceptible  of  tension,  nor 
what  it  is  which  produces  this 
tension. 

If  we  review  the  three  tissues 
which  compose  the  substance 
of  the  lips  of  the  glottis,  from 
the  surface  to  the  depth,  that 
is  to  say,  the  mucous,  the  elastic 
ligament  (vocal  cord)  and  the  muscle  (Fig.  92),  and  seek 
to  discover  which  of  these  three  constitutes  the  vibrating 


Fig.  92. —Vertical  section  of  tlie 
larynx.* 


*  This  figure  plainly  shows  that  the  edges  of  the  glottis  are  essentially 
formed  of  muscular  tissue.  1,  Thyroid  cartilage.  2,  Cricoid  cartilage.  3,  First 
ring  of  the  trachea.  4,  Epiglottis.  5,  Its  median  cushion.  6,  Upper  vocal 
cords.  7,  Lower  vocal  cords.  8,  Morgagni's  ventricles.  9,  Thyro-arytenoid 
muscle  (the  real  vocal  cord,  in  a  physiological  point  of  view).  10,  Lateral  crico- 
arytenoid muscle.    (Bcaunis  and  Bouchard,  "Anatomie  Descriptive.") 


ft 


LARYNX  AND  PRONATION.  355 

body,  we  shall  certainly  not  fix  upon  the  mucous,  which 
forms  a  protecting  envelope,  but  is  not  an  organ  capable  of 
being  stretched  or  of  vibrating.  The  vocal  cord,  although 
it  is  called  a  ligament,  does  not  seem  to  exhibit  the  neces- 
sary conditions  for  constituting  the  vibrating  cord,  as  is  gen- 
erally supposed.  This  ligament  is  composed  of  elastic  tissue, 
that  is,  of  fibres  which  are  not  rectilinear,  but  entangled  in 
every  direction,  so  that,  whichever  way  it  is  drawn,  the  ten- 
sion produced  is  extremely  slight.  In  the  physiological  state, 
however,  this  tension,  which  is  accompanied  by  the  contrac- 
tion of  the  glottis,  can  only  be  produced  by  the  crico-thyroid 
muscle,  which,  we  have  seen,  plays  a  very  insignificant  part 
in  phonation.  The  muscular  tissue  then  remains,  viz.,  the 
thyro-arytenoid  muscle.  Now  the  muscular  tissue  is  very 
susceptible  of  tension.  What  can  be  more  stretched,  or  more 
strongly  elastic,  or  what  more  vibratory  than  a  contracted 
muscle  ?  The  thyro-arytenoid  muscle,  therefore,  in  a  physio- 
logical point  of  view,  constitutes  the  true  vocal  cord,  the  only 
I'eal  vibratory  element  among  the  tissues  which  form  the  lips 
of  the  glottis.  This  vocal  cord  is  stretched,  for  the  purpose 
of  vibration:  this  is  not,  however,  the  effect  of  any  outside 
influence :  it  contracts  of  itself}  The  glottis  apparently  forms 
a  pipe  which  vibrates  by  contraction  and  not  by  tension.  As 
being  the  source  of  sound,  this  organ  is  unequalled  (unique), 
and  cannot  be  imitated  artificially,  since  we  cannot  make 
muscle :  the  lips  (orbicular  muscle  of  the  buccal  orifice)  work 
in  a  similar  manner  in  the  cases  previously  mentioned.* 

We  shall  easily  understand  the  use  of  the  vocal  elastic 
cord,  if  we  consider  what  would  happen  if  the  organ  of  phona- 
tion or  voice  were  composed  only  of  muscle,  covered  with  a 
mucous  surface :  at  each  contraction  of  the  former,  the  latter 
would  form  irregular  folds,  thus  altering  the  sound  of  the 
voice;  this  happens  when  the  smallest  particle  of  foreign 
matter,  whether  mucus  or  any  thing  else,  is  caught  in  the 
glottis.  An  elastic  organ  is  therefore  necessary  to  render  the 
muscle  and  the  mucous  independent  of  each  other,  by  inter- 
posing itself  between  the  two.    This  is  precisely  the  office  of 

*  *'  The  contraction  of  the  internal  thyro-arytenoid  muscle 
causes  the  lower  folds  (lips  of  the  glottis),  which' were  soft  and 
loose  during  respiration,  to  be  transformed;  during  the  emission  of 
the  voice,  into  an  organ -pipe,  whose  rigidity  is  in  proportion  to  its 
tonality.  This  muscle  may  therefore  be  said  to  be  the  accommo- 
dating muscle  of  the  voice."     (L.  Mandl.     1872.) 

2  See  note,  p.  353. 


856  PULMONARY  MUCOUS  TISSUE. 

the  vocal  cord,  and  what  we  have  said  of  its  structure  suffi- 
ciently proves  that  it  is  admirably  adapted  to  this  end.^ 

The  different  degrees  of  contraction  of  the  glottis  have  also 
the  effect  of  increasing  or  diminishing  the  production  of 
sounds :  as  the  glottis  becomes  more  contracted  the  sound 
becomes  sharper,  and  when  it  reaches  the  highest  possible 
pitch,  the  glottis  can  contract  no  more  without  being  entirely 
obliterated  (we  are  speaking  of  the  ordinary  voice  j  there 
appears  to  be  a  special  arrangement  in  regard  to  what  is 
called  the  head-voice^  or  falsetto). 

The  anatomical  arrangement  of  the  parts  obliges  the  vocal 
(anatomical)  cords  to  relax  as  the  glottis  closes.  Yet  if 
these  cords  formed  the  vibrating  organ,  the  sounds  produced 
would  be  lower  in  proportion  to  the  amount  of  closure  of  the 
lips  of  the  glottis;  the  narrowness  of  the  aperture,  it  is  true, 
increases  the  intensity  of  the  current  of  air,  and  may  thus 
help  to  render  the  sounds  higher ;  but  the  whole  process  is 
much  more  simple  if  we  admit  that  it  is  the  muscle  which 
vibrates :  as  in  contracting,  it  contributes  to  the  obliteration 
of  the  glottis,  and  even  serves  to  close  it  entirely;  so 
when  it  becomes  more  contracted,  or  stretched,  it  can  vibrate 
more  readily. 

The  elastic  cords^  which  are  called  vocal,  peiform  only  an 
accessory  part  in  phonation,  that  of  serving  as  an  intermedium 
between  the  mucous  membrane  and  the  muscle ;  they  no  more 
prevent  the  muscle  from  vibrating  than  the  soft  parts  surround- 
ing the  orbicularis  of  the  lips  prevent  this  muscle  from  vibrat- 
ing, as,  for  instance,  when  playing  on  the  horn. 

The  vibrations  of  the  thyro-arytenoid  muscle  are  also 
assisted  by  the  ventricles  of  the  larynx,  whose  only  office  is 
to  give  this  muscle  greater  freedom  in  working  (Fig.  92). 

JParts  connected  with  the  Organs  of  the  Voice. — The  sound 
produced  by  the  glottis  is  increased  by  the  vibrations  of  those 
portions  of  the  air-tube  which  are  above  and  below  the 
larynx.  Special  movements,  also,  take  place  in  these  parts, 
during  the  production  of  sounds.  Thus,  dming  the  emission  of 

'  See  Henle,  "  Handbuch  der  Systematischen  Anatomie  des 
Menschen."  1866,  Vol.  II.  p.  259.  *' The  muscular  fibres  so 
encroach  upon  the  vocal  cords,  and  are  so  closely  united  to  the 
elastic  tissue,  that  we  cannot  suppose  that  the  elastic  fibres  vibrate 
alone,  and  that  the  muscular  fibres  withdraw  from  the  folds  of  the 
mucous.  .  .  .  The  chief  utihty  of  the  elastic  tissue  consists  in  its 
power  of  contracting  without  forming  folds  and  wavy  lines,  as  is 
the  case  with  some  ligaments  of  the  vcrtubral  column.'* 


LARYNX  AND  PRONATION.  357 

the  higher  notes,  the  larynx  rises,  the  laryngeal  muscles  being 
contracted  for  this  purpose  and  the  head  thrown  back ;  while, 
for  the  lower  notes,  the  larynx  descends  and  the  chin  is  de- 
pressed. These  are  well-known  movements,  and  a  patient 
examined  with  the  laryngoscope  is  sometimes  made  to  utter 
high  notes,  because  exploration  of  the  larynx  is  more  readily 
performed  when  it  is  elevated.  Attempts  have  been  made 
to  explain  these  phenomena  by  comparing  them  with  those 
produced  in  wind-instruments.  In  the  first  instance,  the  part 
under  the  glottis  was  supposed  to  be  elongated,  and  the  part 
above  the  glottis  contracted,  and  vice-versa^  in  the  second  or 
emission  of  high  notes.  This  explanation,  however,  is  ren- 
dered useless  by  the  fact  that  the  same  phenomena  are  ob- 
served when  we  produce  the  sound  in  inspiration ;  thus, 
although  the  physical  performance  of  the  organs  is  reversed, 
the  larynx  always  rises  in  the  upper  notes  and  falls  in  the 
lower. 

The  elevation  of  the  larynx  may  be  much  more  satisfac- 
torily explained  by  considering  that  the  walls  of  the  trachea 
act  as  a  resonnnt  organ,  and  that,  consequently,  in  order  to 
heighten  a  certain  sound,  they  mu«t  be  in  a  state  of  peculiar 
tension,  for  the  same  elastic  wall  does  not  vibrate  indiffer- 
ently with  all  sounds :  its  tension  must  be  modified  in  differ- 
ent cases.  The  higher  the  note,  the  more  tense  the  resonant 
parts  are. 

The  entire  nasal  system,  consisting  of  the  nasal  chambers 
and  the  frontal,  ethmoidal,  and  maxillary  sinuses,  is  connected 
with  these  organs  of  sound.  These  cavities  are  not  intended 
for  secretions ;  but,  on  account  of  their  coats  being  formed 
of  somewhat  delicate  elastic  lamellae,  they  readily  vibrate. 
Any  injury  to  these  organs  considerably  modifies  the  tone  of 
the  voice.  The  cartilages  of  the  nose  are  also  resonant 
organs,  as  everybody  knows  that  when  they  are  hindered 
from  vibrating  the  tone  of  the  voice  is  altered  in  a  peculiar 
manner. 

The  vibration  of  the  trachea,  the  bronchi,  the  lungs,  and 
the  cage  of  the  thorax,  also  serves  to  intensify  the  sounds 
produced  by  the  larynx.  The  voice  undergoes  a  change  in 
diseases  of  the  trachea,  the  bronchi,  and  the  lungs. 

The  aHiculation  of  speech,  which  differs  greatly  from  the 
simple  cri/,  or  sound  made  by  the  larynx,  are  almost  entirely 
produced  by  the  working  of  these  sonant  parts,  and  chiefly 
by  modifications  in  the  apertures  of  the  lips  and  the  back 
part  of  the  throat.. 


858  PULMONARY  MUCOUS  TISSUE. 

Voice  and  Speech. — The  sound  produced  at  the  glottis  is 
ouly  an  inarticulate  sounds  differing  only  in  intensity.,  pitch., 
and  tone ;  yet  this  glottid  sound,  by  the  re-enforcement  of 
certain  of  its  characteristics  at  the  buccal  and  nasal  cavities, 
and  by  the  union  with  other  sounds  produced  at  these  points, 
lacquires  special  features  constituting  the  voice  and  speech 
properly  so-called  (see  Organs  of  the  Senses  {Hearing)  for  tho 
explanation  of  the  words  intensity y  pitchy  tone,  sounds,  etc.). 

The  intensity  of  the  sound  j^roduced  in  the  glottis  depends 
on  the  force  with  which  the  expiratory  current  of  air  strikes 
the  edges  of  the  glottis  when  so  arranged  as  to  emit  any 
decided  sound ;  this  intensity  depends  essentially  on  the  de- 
velopment and  the  elasticity  of  the  lung,  the  breadth  of  the 
thoracic  cage,  and  the  force  of  the  expiratory  muscles. 

The  pitch  of  the  sound  produced  by  the  vocal  lips  increases 
in  proportion  to  their  length  and  tensio7i  (or  contraction) ; 
thus  the  human  voice  performs  the  gamut  or  scale  in  passing 
from  the  lower  notes  to  the  higher ;  it  even  forms  two  series 
of  scales,  the  lower  of  which  is  generally  designated  under 
the  name  of  chest  register  {chest  voice),  and  the  sharper  and 
higher  under  that  of  head  register  (head  voice).  These  ex- 
pressions have  no  meaning  in  a  physiological  point  of  view, 
since  the  voice  is  formed  in  the  glottis  in  both  cases ;  but  what 
has  given  rise  to  them  (and,  in  a  certain  sense,  justifies  the 
use  of  them)  is  the  sensations  experienced  during  the  emission 
of  either  the  so-called  head  or  chest  voice,  the  accompanying 
vibrations  being  more  strongly  marked  in  the  walls  of  the 
chest  in  the  one  instance,  and  in  the  supra-laryngeal  cavities 
in  the  other.  According  to  Mandl,  the  essential  modification 
in  the  glottis  which  produces  the  emission  of  sounds  in  the 
two  registers,  consists  in  the  fact  that,  in  the  case  of  the  chest 
voice,  the  orifice  of  the  glottis  is  open  and  vibrates  through- 
out its  w^hole  extent,  while  in  that  of  the  head  voice  (or 
falsetto)  the  orifice  is  open  and  vibrates  only  in  the  interliga- 
mentous  part ;  the  entire  intercartilaginous  portion  is  then 
closed,  while  the  superior  vocal  cords  sink,  and  are  adjusted 
to  the  inferior  cords,  covering  a  considerable  part  of  them  in 
such  a  manner  as  to  diminish  the  extent  of  the  vibrating  part 
(an  effect  resembling  that  produced  by  the  tongues  employed 
in  the  pipes  of  an  organ)  .^ 

The  human  voice  has,  therefore,  generally  a  range  of  two 

*  See  also  Ch.  Bataille,  *'  Nouvelles  Recherches  sur  la  Phona- 
tion."     Paris,  1861. 


I 


i 


LARYNX  AND  PEON  ATI  ON.  359 

octaves,  and  according  to  whether  these  two  octaves  belong 
to  the  upper  or  lower  part  of  the  scale  of  musical  sounds,  the 
human  voice  has  been  classified,  beginning  with  the  lowest, 
into  the  bass  voice  (from  fa  to  rCg),  the  barytone  (from  la  to 
fag),  the  tenor  (from  dog  to  la^),  the  contralto  (from  mig  to 
do^),  the  mezzo-soprano  (from  solg  to  mi^),  and  the  soprano 
(from  sig  to  sol^),  the  three  latter  being  women's  voices.  The 
differences  between  them  are  principally  owing  to  variations 
in  the  length  of  the  lips  of  the  glottis ;  this  length  is  repre- 
sented in  man  by  the  number  25,  in  woman  by  20,  and  by  15 
in  eunuchs,  their  voice  being  extremely  high. 

A  child's  voice  is  very  high,  the  glottis  being  smaller  than 
that  of  the  adult.  The  change  in  the  voice  takes  place  at 
the  age  of  puberty,  the  development  of  the  larynx  causing 
the  voice  to  become  an  octave  lower  in  the  case  of  boys,  and 
two  notes  only  in  that  of  girls.  In  old  age,  the  ossification 
of  the  cartilages,  and  the  atrophy  of  the  muscular  fibres  (?) 
cause  the  voice  to  become  still  lower,  while  its  intensity  is 
also  diminished;  thus  tenors  become  barytones  (L.  Mandl). 

The  t07ie  of  tlie  voice  is  first  produced  by  the  lips  of  the 
glottis  itself.  Ilelmholtz  has,  we  know,  demonstrated  that 
the  t07ie  (see  Organs  of  the  Senses^  Hearing)  is  due  to  the 
fact  that  the  sounds  which  appear  to  us  so  simple  are  really 
composed  of  a  fundamental  note,  and  several  accessory 
netes,  called  harmonics  (Sauveur).  The  varied  combina- 
tion of  these  harmonic  notes,  in  different  instruments,  con- 
stitutes their  special  tone.  The  vocal  lips,  like  the  membranous 
pipes,  beside  the  fundamental  vibration  of  one  sound,  exhibit 
partial  vibrations  which  give  rise  to  various  harmonics  of  this 
note :  whence  the  different  tones  of  the  note  produced  by 
the  glottis.  What,  however,  especially  marks  the  tone  of 
the  voice,  is  the  manner  in  which  these  harmonic  notes  are 
reinforced  in  the  cavities  and  vibrating  edges  above  the 
glottis  (the  pharynx,  mouth,  nasal  chambers,  etc.),  so  as  to 
impress  their  peculiar  features  upon  the  voice  (see  p.  357). 

By  studying  these  harmonic  notes  as  being  the  means  by 
which  the  tone  of  the  voice  is  produced,  Willis,  Wheatstone, 
Bonders,  Du  Bois-Reymond,  and  especially  Helmholtz,^  have 

'  See  Helmholtz,  **  Theorie  Physiologique  de  la  Musique." 
Trad.  fran.  par  Gueroult,  Paris,  1868. 

Laugel,  "  La  Voix,  I'Oreille,  et  la  Musique."  D'apres  les 
travaux  de  Helmholtz.  Li  "  Eevue  des  Deux-Mondes."  Mai, 
1867. 


PULMONARY  MUCOUS  TISSUE. 

been  enabled  to  discover  the  mechanism  by  which  the  vowels 
are  produced.  The  vowels  are  essentially  notes  produced 
by  the  passnge  of  the  air  through  the  pharyngeal  and  buccal 
cavities;  these  are  arranged  in  a  special  manner,  and,  con- 
sequently, resound  differently  as  each  vowel  is  pronounced. 
When  a  vowel  is  i)ronounced  in  a  whisper,  the  glottis  takes 
no  part  in  tlie  process,  the  sound  being  produced  simply  by 
the  passage  of  the  air  through  the  supra-glottidal  cavities, 
which  at  that  moment  are  so  arranged  as  to  give  utterance 
to  the  vowel  in  question  ;  when  the  same  vowel  is  pronounced 
aloud,  the  supra-glottidal  cavities,  arranged  as  before,  produce 
the  effect  of  reinforcing  those  harmonics  existing  in  the 
Bound  made  in  the  glottis,  which  exactly  correspond  with 
those  of  the  vowel  to  be  pronounced.  In  other  words,  the 
buccal  and  pharyngeal  cavities  act  as  sounding  boards,  which 
may  be  variously  harmonized. 

We  cannot  carry  this  analysis  any  farther  here ;  it  belongs 
to  the  domain  of  pure  physics,  and  we  will  only  add  that  the 
form  assumed  by  these  cavities  for  the  utterance  of  the  differ- 
ent vowels,  has  been  clearly  ascertained,  and  that  when  the 
cavities  are  properly  arranged,  if  the  wind  from  a  pair  of 
bellows  be  made  to  pass  before  the  mouth,  even  though  the 
breath  be  held  back,  sounds  are  heard  exactly  resembling 
vowels  pronounced  in  a  whisper.  In  general  it  may  be  said 
that  "the  longitudinal  diameter  of  the  pharyiigo-hucQal 
camty  is  reduced,  and  its  transverse  diameter  increased  by 
the  vowel-sounds  ah,  a,  and  e  (a,  e,  i) ;  while  in  pronouncing 
the  vowel-sounds  o  and  u,  the  longitudinal  diameter  is  in- 
creased and  the  transverse  diameter  diminished.  The  move- 
ments of  the  different  parts  of  the  cavity  follow  this  general 
disposition.  The  lips  make  a  horizontal  movement,  wliich  is 
more  and  more  decidedly  antero-posterior  in  the  case  of  the 
three  lirst  vowels,  and  anterior  in  that  of*  the  two  latter.  In 
pronouncing  o  and  w,  the  tongue  is  drawn  backward,  while 
in  a  and  e,  it  is  more  or  less  thrown  forward.  The  move- 
ments of  the  cheeks,  the  velum  of  the  palate,  the  uvula,  and 
the  pillars  of  the  fauces,  all  unite  in  carrying  out  this  general 
arrangement,  etc.  etc."  (Mandl,  op.  cit.). 

The  consonants,  which  form  the  second  element  of  articu- 
late speech,  are  not  sounds,  like  the  vowels,  but  rather  irreg- 
ular vibrations,  too  confusedly  mingled  to  be  separately 
distinguished  (see  Hearing)  ;  they  are  sounds  which  cannot 
be  distinctly  heard  by  themselves,  but  differ  by  the  manner 
in  which  they  begin  or  finish  the  utterance  of  a  vowel.     The 


LARYNX  AND  PRONATION.  361 

consonants,  therefore,  can  only  be  pronounced  by  being  joined 
with  a  vowel,  whence  their  name  (cum  sonare).  When  a 
vowel  is  uttered,  the  cavities  of  the  mouth  and  pharynx  are 
so  arranged  as  to  present  certain  obstructions  to  the  air 
which  produces  the  vowel,  and  the  interruption  to  these 
latter  causes  the  more  or  less  loud  sound  of  the  consonants. 

The  consonants  are  labial,  lingual,  or  guttural,  according 
as  the  obstruction  is  found  in  the  lips,  the  tongue,  the  velum 
of  tlie  palate,  or  the  pharynx ;  and  in  accordance  with  the 
force  employed  to  overcome  the  obstruction,  whether  by  a 
sort  of  explosion,  by  vibratory  friction,  or  by  a  trembling 
movement,  we  have  explosive  labials  (^, />),  resonant  labials 
(f,  V,  m),  explosive  {t,  d)  and  trembling  Unguals  (r),  explosive 
gutturals  {k,  g),  resonant  gutturals  (j  and  cA,  especially  in 
German),  and  trembling  gutturals  (the  guttural  r).  In  some 
languages,  especially  the  Arabic,  the  gutturals  are  very 
marked,  as,  for  instance,  the  sound  which  we  designate  as 
ha,  and  which  appears  to  be  produced  by  some  obstacle 
situated  as  low  down  as  the  glottis.  It  was  while  seeking  to 
discover  the  mechanism  by  which  the  really  guttural  sounds 
of  the  Arab  tongue  are  produced  that  Czermak  invented  the 
laryngoscope  which  is  now  so  universally  employed  for  the 
exploration  of  the  larynx. 

The  labial  consonants,  especially  the  explosive  labials  {h, 
jo,  m),  are  the  most  easy  to  pronounce,  on  account  of  the 
simplicity  of  the  movements  required :  they  are  the  first 
uttered  by  children  (papa,  mamma,  etc.),  and  are  those  which 
are  most  easily  taught  to  certain  animals,  and  are  naturally 
produced  in  bleating  (L.  Mandl). 

This  combination  of  phenomena,  by  means  of  which  a 
sound  is  uttered  by  the  glottis,  modified  by  the  pharyngeal 
and  buccal  cavities  in  such  a  manner  as  to  represent  a  vowel, 
nu^  joined  to  certain  sounds,  produced  in  the  same  cavities, 
and  which  form  consonants,  serves  to  constitute  the  articu- 
late voice,  while  the  intelligent  combination  of  vowels  and 
consonants  in  syllables,  and  of  syllables  in  words,  constitutes 
speech.  In  spoken  words,  the  variations  in  pitch  of  the  syl- 
lables are  not  strongly  marked ;  in  singing,  on  the  contrary, 
the  syllables,  especially  the  vowels,  which  form  their  essential 
element,  are  produced  with  considerable  and  harmoniously 
arranged  variations  in  pitch. 

Innervation  of  the  Laryngeal  Organ.  —  The  organ  of. 
phonation  of  the  larynx  is  dependent  on  the  inferior  laryn- 
geal nerve,  which  appears  to  come  from  the  pueumo-gastric, 


S62  PULMONARY  MUCOUS  TISSUE, 

but  really  represents  the  series  of  fibres  which  this  great 
nerve  trunk  borrows  from  the  accessory  of  Willis,  or  spinal 
nerve  (internal  branch  of  the  spinal  nerve).  Section  of  the 
spinal  nerve  entirely  destroys  the  voice :  this  might,  there- 
fore, be  called  the  vocal  nerve.  It  is  remarkable  that  the 
other  branches  of  the  spinal  nerve  (the  external  branch)  lead 
to  two  superficial  and  well-known  muscles,  the  stern o-cleido- 
mastoideus  and  the  trapezius,  both  which  muscles  play  an 
important  part  in  expressions  by  signs,  or  what  may  be  called 
the  language  of  the  neck  and  shoulders  (shrugging  the  shoul- 
ders, making  a  sign  of  negation  with  the  head,  etc.).  The 
epinal  nerve  thus  appears  to  be  the  nerve  of  mimicry  and 
phonation. 

While  serving  for  purposes  of  mimicry,  the  external  branch 
of  the  spinal  nerve  takes  an  active  though  indirect  part  in 
phonation :  this  nerve  innervates  the  sterno-mastoideus  and 
trapezius  muscles,  when,  during  sonorous  expiration,  these 
muscles  contract  for  the  purpose  of  preventing  the  thoracic 
cage  from  sinking  suddenly.  This  peculiarity  is  easily  ob- 
served  in  singers,  in  whom  it  constitutes  what  Manal  calls 
the  vocal  struggle  ;  which  consists  in  a  struggle  between  the 
spinal  nerve  and  the  expiratory  movement ;  CI.  Bernard  has 
demonstrated,  by  numerous  vivisections,  that  the  spinal 
nerve  plays  the  same  part  in  animals  during  the  utterance  of 
a  prolonged  cry,  and  thus  has  proved  that,  in  a  physiological 
point  of  view,  the  spinal  nerve  is  not  the  accessory^  but  rather 
the  antagonist  of  the  pneumo-gastric  nerve,  since  it  produces, 
both  in  the  glottis  (by  its  internal  branch)  and  the  walls  of 
the  thorax  (by  its  external  branch),  movements  which  are 
opposed  to  those  of  respiration. 

It  is  now  proved  that  the  nerve  centre  of  phonation  is 
situated  in  the  spinal  cord ;  it  is  plain  that  this  centre  is  not 
found  in  the  brain,  for  anencephalous  patients  have  been 
known  to  scream  under  the  influence  of  external  excitation 
or  internal  pain.  The  centre  of  articulate  speech^  or  rather, 
the  centre  of  the  memory  ofwords^  appears  to  reside  in  the 
brain ;  attempts  have  been  made  to  fix  its  seat  in  the  anterior 
lobes,  but  the  observations  made  on  this  subject  are,  so  far, 
contradictory.  Both  centres  are  independent  of  each  other, 
for  a  cry  may  be  easily  uttered  when  articulation  is  very 
difficult.     Amnesia^  or  the  loss  of  memory  of  words,  there- 

*  See  Aug.  Voisin,  Art.  "  Amn^sie,"  in  *'  Nouveau  Diet,  de 
Mdd.  et  de  Chirur.  Prat."     Vol.  II.  p.  53. 


LARYNX  AND  PHONATION.  363 

fore,  must  be  distinguished  from  aphasia^  or  the  loss  of  power 
to  pronounce  them.  The  patient  suffering  from  aphasia  can 
still  write  his  thoughts,  while  in  amnesia  he  can  only  express 
himself  by  drawing  a  representation  of  the  objects  which  he 
desires. 

We  will  remark,  in  conclusion,  that  the  working  of  tlie 
organs  of  the  voice,  in  regard  to  language,  is  closely  con- 
nected with  that  of  hearing;  as  speech  can  only  come  after 
hearing,  a  child  learns  to  talk  solely  by  repeating  the  sounds 
which  he  hears  every  day.  A  person  who  has  never  heard, 
is  unable  to  speak,  and  Bonnafont  has  proved  that  any  one 
who  has  heard  and  spoken  up  to  the  age  of  three,  four,  or 
even  five  years,  and  then,  by  any  accident,  entirely  lost  his 
hearing,  will  gradually  lose  the  power  of  speech,  until,  in  a 
few  years,  he  will  be  scarcely  capable  of  uttering  any  articu- 
late sounds.  We  may,  therefore,  say  that  a  person  who  is 
deaf  and  dumb  from  his  birth  is  dumb  only  because  he  is 
deafi 

*  See  J.  P.  Bonnafont,  *'  Traite  Theorique  et  Pratique  des 
Maladies  de  1' Oreille.''     2d  edition.     Paris,  1873,  p.  609. 

It  must,  however,  be  remarked  that  persons  who  are  deaf  can 
be  taught  to  articulate  words  through  the  medium  of  sight  and 
mimicry.    [Am.  ed.J 


PART    EIGHTH. 
EXTERNAL    INTEGUMENT. 

The  Skin. 

The  skin  forms  one  of  the  principal  surfaces  by  means  of 
which  the  organism  comes  in  contact  with  the  ambient 
mediums :  therefore,  we  shall  proceed  to  study ;  first  its  struc- 
ture, and  then  its  functions  in  regard  to  the  exchanges  which 
take  place,  either  from  within  to  without,  or  from  without  to 
within ;  and  finally  its  sensibility,  or  the  power  which  it  has 
of  conveying  the  impression  of  the  outer  world  to  the  origins 
of  the  sensory  or  centripetal  nerves. 

I.  Stimcture  of  the  shin  —  Epidermic  productions. 

«.  Dermis  and  Epidermis. — The  skin  (Fig.  93)  is  formed 
of  the  dermis  and  the  epidermis.  The  dermis  forms  a  sub- 
stratum of  connective  and  elastic  tissue,  serving  as  a  support 
for  the  most  important  part  of  the  cutaneous  covering,  the 
epidermis,  and  contains  blood-vessels,  nerves,  and  the  glan- 
dular organs  produced  by  its  deep-seated  vegetation.  The 
dermis  :ilso  contains  smooth  muscular  elements,  unequally 
distributed  in  different  parts :  in  the  skin  of  the  scrotum  these 
elements  form  a  continuous  layer  (dartos).  In  the  nipple, 
they  form  a  special  erectile  organ ;  above  all,  they  are  joined 
to  the  follicles  of  the  hair,  which  they  can  straighten ;  the 
contraction  of  these  muscles,  under  the  influence  of  cold,  for 
instance,  produces  the  sensation  known  as  having  onds  flesh 
creep,  goose-flesh.  This  sensation,  as  well  as  the  erection  of 
the  nipple,  are  purely  muscular  phenomena,  and  in  no  way 
resemble  the  erection  of  the  erectile  vascular  tissues:  the 
nipple,  for  instance,  has  transverse  muscular  fibres,  the  con- 
traction of  which  increases  its  length  by  diminishing  its 
thickness;  in   the  case  of  the  phenomenon  of  goose-flesh, 


THE  SKIN. 


365 


the  smooth  muscles  straighten,  causing  a  projection  of  the 
pilous  bulbs  to  which  they  are  joined. 


Fig.  93.— Diagram  of  the  skin  in  general.* 

The  epidermis  forms  the  essential  part  of  the  skin :  it  is 
this  part  which  first  appears  in  the  embryo,  at  the  same  time 
with  the  epithelium  of  the  digestive  tube,  the  dermis  being 
subsequently  formed  and  or- 
ganized.    This  cellular  cov-     r^<5^i??:;?^==^=^^p=='^^^:rr:^5i^ 3 

ering  is  composed  of  several 
layers  of  globules,  the  deepest 
being  columnar  or  cylindri- 
cal, like  those  of  the  intesti- 
nal mucous,  and  constituting 
what  is  called  the  layer  of  Fig  94, 
Malpighi  (or  mucous  layer, 
rete  or  stratum  mucosum)  ;  in  the  more  superficial  zones,  the 


Diagram  of  the  layers  of  the 
epidermis.t 


*  Section  from  the  scalp  (Gurlt).  a,  Epidermis.  6,  Stem  of  a  hair, 
c,  /j  g,  Sudoriparous  gland,  e,  d,  Sebaceous  gland  and  its  excretory  tube,  h,  i, 
Adipose  tissue.    ,;,  Bulb  of  the  hair. 

t  l,Malpighi"'s  layer.  2,  Layer  of  cells  whose  dimensions  are  nearly  equal 
In  all  directions.  3,  buperlicial  layer  of  flattened  corneous  cells,  which  have  lost 
their  nuclei. 


866  EXTERNAL  INTEGUMENT. 

form  of  the  cells  changes  successively,  from  being  polyhedral 
and  nearly  of  the  same  dimensions  on  all  sides,  and  becomes 
first  broader,  and  finally  quite  flat,  being  reduced  to  a  simple 
band :  these  successive  modifications  of  form  may  be  toler- 
ably well  represented  by  a  series  of  parabolic  lines  placed 
near  each  other,  running  in  opposite  directions,  and  crossing 
each  other  more  or  less  obliquely  according  to  the  level  of 
the  layers  of  cells  with  which  their  points  of  intersection 
correspond  (Fig.  94). 

b.  Life  of  the  globular  Elements  of  the  Epidermis. — ^Be- 
side the  change  oi  form^  an  important  element  of  difierence 
between  the  layers  is  their  change  in  strueture^  in  composi- 
tion :  the  malpighian  layer,  and  the  few  layers  next  to  it,  are 
formed  of  actual  globules,  that  is,  albuminous  masses  of 
protoplasm,  capable  of  being  dissolved  into  mucus,  and  are,  in 
short,  living  globular  elements  ;  above  these  layers,  however, 
the  structure  suddenly  changes,  and  we  find  only  dried-up, 
ehrivelled  or  flattened  cells,  which  have  lost  the  greater  part 
of  their  albumen :  they  are,  in  short,  corneous  cells  (corneous 
layer),  the  albumen  being  oxidized  and  changed  into  ker- 
atine.^ 

Beside  these  difierences  in  structure  and  composition  be- 
tween the  two  parts  of  the  epidermis,  we  find,  as  we  should 
expect,  quite  as  marked  a  difference  in  their  physiological 
functions.  The  superficial  corneous  or  horny  cells  may  be 
considered  as  no  longer  living:  the  globules  of  the  deep 
layers  are  essentially  alive ;  that  is,  they  react  under  the  in- 
fluence of  excitants,  and  actually  give  rise  to  inflammatory 
phenomena:  thus,  if  heavy  pressure  be  long  continued,  the 
deep  layer  is  metamorphosed  and  liquefied,  giving  out  either 
a  simple  fluid,  containing  a  few  nuclei  (blister,  phlyctence)^ 
or  else  purulent  matter ;  cold  and  extreme  heat  produce  the 
same  effect,  as  do  also  some  chemical  irritants  (such  as  can- 
tharidine)^  known  under  the  general  name  of  vesicants  or 
vesicatories ;  in  this  case  the  middle  layer  of  the  epidermis  is 
liquefied,  forming  a  fluid  mass  which  raises  the  cuticle  or 
corneous  layer.  If  this  layer  be  removed,  the  serum  will 
flow  out,  and  a  white  covering  be  seen  spread  over  the  der- 
mis. This  is  the  malpighian  layer;  and  is  ready  to  form 
again,  by  its  proliferation,  the  various  layers  of  the  normal 

^  Keratine,  which  is  a  substance  peculiar  to  the  hair,  nails,  and 
hoofs,  really  forms  a  separate  element,  being  insoluble  in  potash, 
unlike  other  organic  substances  (Ch.  Robin) . 


THE  SKIN.  367 

epidermis ;  if,  however,  the  irritating  influence  be  continued, 
the  malpighian  layer  itself  resumes  the  embryonic  globular 
form,  and  by  its  proliferation  gives  rise  to  the  formation 
of  pus. 

This  deep  and  essentially  living  layer  of  the  epidei-mis, 
also  gives  rise  to  neoplasms  of  the  tissue,  or  the  different 
forms  of  epithelial  or  cancroid  cancers.  In  the  malpighian 
layer  are  found  the  pigment  granules  or  corpuscles,  which 
shades  the  color  of  the  skin  in  the  colored  races  and  in 
some  integuments  (scrotum,  the  areola  of  the  nipple,  etc.). 
This  pigment  of  the  rete  malpighianwm^  appears  only  after 
bu-th.  In  the  negi-o,  however,  the  edges  of  the  nails,  the 
areola  of  the  nipple,  and  the  genital  parts,  begin  to  assume  a 
dark  tinge  on  the  third  day,  and  by  the  fifth  or  sixth,  the 
black  color  has  spread  over  the  whole  surface  of  the  body. 
The  base  of  the  umbilical  cord  also  has  a  peculiar  brownish 
hue  at  birth.  Researches  by  Sappey,  however,  show  that  the 
deep  layers  of  the  epidermis  always  contain  a  small  quantity 
of  pigment ;  the  differences  of  complexion  observed  between 
different  races  are  only  due  to  the  larger  or  smaller  quantity  of 
this  pigment:  various  influences  may  heighten  its  development 
in  the  white  races;  such,  for  instance,  as  the  prolonged  action 
of  heat;  in  this  case  the  solar  rays  do  not  give  birth  to 
pigmentary  granulations,  as  a  new  element,  but  simply  occa- 
sion  the   hypertrophy  of  those  which  already  exist  (Sap- 

pey).* 

The  other  layers  are  offshoots  from  the  malpighian  layer ; 
its  globules  multiply  constantly,  and,  by  means  of  this  physi- 
ological proliferation,  the  globular  elements  which  have 
formed  a  part  of  the  primitive  layer,  gradually  withdraw  from 
the  dermis,  and  form  a  succession  of  layers,  the  oldest  of 
which  are  always  nearest  the  surface.  When  these  globules 
extend  a  certain  distance  from  the  dermis,  they  appear  to  fall 
suddenly  into  decay,  and  here  the  line  is  drawn  between  the 
corneous  layer  and  the  rest  of  the  epidermis ;  this  sudden  death  - 
is  the  fate  common  to  all  cells  (excepting,  perhaps,  in  such 
growths  as  the  nails,  the  globules  of  which  always  preserve 
their  nuclei),  and,  it  appears  from  what  we  have  seen,  to  the 
epithelial  cells  also  (intestine).  These  sudden  changes  are 
not  surprising,  in  some  cases  being  much  more  niarked: 
instances  have  been  known  in  which  the  hair,  under  the  in- 

*  See  L.  H.  Farabeuf,  **  De  TEpiderme  et  des  Epitheliums." 
Paris,  1873,  p.  265. 


368  EXTERNAL  INTEGUMENT. 

fluence  of  some  mental  shock,  has  changed  its  color  almost 
instantaneously ;  and  if  this  does  not  indicate  the  existence 
of  vitality  in  the  elements  of  the  hair,  it  proves  at  least  that 
sudden  chemical  modifications  may  be  produced  in  them  by 
certain  states  of  the  nerves,  acting,  either  directly,  or  by 
means  of  the  blood  and  vessels. 

The  corneous  layers  thus  produced  are  destined  to  be 
separated  from  the  epidermis,  and,  consequently,  to  fall  into 
decay,  exactly  as  we  have  seen  in  the  epithelium  of  the  intestine. 
In  the  present  instance,  however,  the  decaying  layers  do  not 
take  the  form  of  mucus,  or  more  or  less  albuminous  flakes,  but 
appear  as  small  scales  or  pellicles,  the  remains  of  dried-up 
cells.  The  part  of  the  epidermis  nearest  to  the  surface,  is 
formed  of  these  layers  of  fragmentary  detritus,  just  ready  to 
fall:  this  is  what  is  called  the  furfuraceous  layer,  which  falls 
off  by  slight  friction.  Pathological  causes  may  sometimes 
increase  this  furfuraceous  desquamation,  and  as  these  epithe- 
lial remains  contain  transformed  albumen  (keratine),  sulphur, 
iron,  etc.,  in  such  a  case  the  organism  suffers  an  actual  loss ; 
this  is  the  reason  that  squamous  diseases  are  so  dangerous 
and  produce  such  exhaustion.  We  have  also  seen  that  if  the 
epithelium  dissolves  into  mucus  in  too  large  quantities,  seri- 
ous pathological  conditions  follow,  such  as  bronchitis^  and 
catarrhs  in  general.  It  may  therefore  be  said  that  what  is 
called  a  pityriasis^  or  desquamation,  in  the  case  of  the  skin, 
is  a  catarrh  in  that  of  a  mucous  surface. 

We  have  seen  that  the  desquamation  of  the  epidermis  does 
not  generally  give  rise  to  a  fluid  like  that  from  the  mucous 
tissue ;  there  are,  however,  some  less  exposed  parts  of  the 
skin,  whose  desquamation  is  less  dry,  and  closely  resem- 
bles the  corresponding  product  of  the  mucous  tissue ;  such 
are  the  arm-pit,  the  fatty  desquamation  of  the  skin  of  the 
gland,  and  of  the  inner  surface  of  the  prepuce  {smegma  proe- 
putii)  ;  we  shall  also  find,  in  the  sebaceous  gknds,  saccular 
recesses  of  epidermis;  as  these  fall  into  decay,  they  become 
gradually  more  and  more  liquid,  being  finally  changed,  in 
the  sudoriferous  glands,  into  an  extremely  thin  liquid.  The 
desquamation  of  the  epidermis,  in  the  foetus,  is  neither  dry 
nor  corneous;  it  is  distinguished  by  its  fatty  degeneration 
(vernix  caseosa),  similar  to  the  smegma  prgaputii ;  this  fatty 
degeneration  continues  after  birth  in  certain  parts,  especially 
those  which  are  formed  last,  such  as  the  top  of  the  head,  and 
especially  about  the  median  line  and  the  great  fontanel,  the 
skin  of  which  appears  at  birth  to  be  not  yet  fully  matured. 


THE  SKIN. 


86U 


c.  Growths  of  the  Epidermis.  —  Besides  this  desquamative 
vegetation,  the  epidermis  is  also  the  seat  of  special  growths 
whose  purpose  it  is  to  produce  more  or  less  permanent  organs, 
such  as  hair^  nails,  feathers  and  other  corneous  products. 
The  formation  of  the  hair  is  the  type  of  all  the  rest :  the  be- 
ginning of  this  growth  is  an  off-shoot  of  the  epidermis  of  the 
rete  malpighianum,  which  sinks  into  the  dermis,  and  here 
forms  a  kind  of  sac,  like  the  finger  of  a  glove,  more  or  less 
resembling  a  bottle  in  shape  {pilous  follicle)  ;  at  the  bottom 
of  this  cul-de-sac,  which  grows  downwards,  a  shoot  (Fig.  95) 
of  the  epidermis  is  formed,  which  now  growing  upwards, 
towards  the  surface,  lengthens  grad- 
ually, passes  along  the  follicle  {root 
of  the  hair),  and,  coming  out,  forms 
a  more  or  less  decided  protuberance 
outside  (stem  of  the  hair:  hair, 
down).  These  growths  are  all  com- 
posed of  globular  elements  similar 
to  those  of  the  corneous  layer,  being, 
like  this,  extremely  hygroscopic; 
this  hygroscopy  is  considerably  di- 
minished by  means  of  the  fatty 
matter  which  the  sebaceous  glands 
spread  over  the  skin,  and  with 
which  they  cover  the  hair  as  soon 
as  it  is  developed,  these  glands,  as 
we  shall  see,  opening  into  the  upper 
part  of  the  pilous  follicles.  Some 
kinds  of  hair  (as  the  tactile  hair  of 
the  muzzle  of  the  dog  and  cat)  exhibit  on  the  inside  a  dermic 
papilla,  which  rises  to  a  certain  point  in  the  medulla  or  pith. 
This  papilla  is  extremely  vascular :  it  therefore  would  appear 
probable  that  it  also  contains  nervous  elements  constituting 
it  an  organ  of  touch,  which  has  been  proved  to  be  the  case 
(J.  Dietl,  by  his  experiments  on  the  hair  of  an  ox).^ 


Fig  95  —  Diagram  of  a  deep  fol- 
licle of  the  epidermis,  or  forma- 
tion of  a  hair  and  of  sebaceous 
glands* 


*  See  M.  Duval,  '*  Note  pour  servir  k  I'Etude  de  quelques 
Papilles  vasculaires"  (papilles  des  polls).  "Journal  de  1' Ana- 
tomic."     1873. 

J.  Dietl,  "  Untersuchungen  iiber  Tasthaare."  (In  "  Sitzungs- 
berichte  der  Akademie  der  Wissenschaften."     Wien.,  1872,  p.  62.) 

*  A,  Bottom  of  the  follicle  in  which  is  formed  the  hair-knob  [bulbe  pileux). 
B,  B,  Lateral  pouches,  origins  of  the  two  sebaceous  glands.    C,  Extremity  of  the 

Jroung  hair,  just  emerging  from  its  follicle.    1,  Malpighi's  layer.    2,  Middle 
ayer  of  the  epidermis.    3,  Corneous  layer  of  the  epidermis. 

2A 


370  EXTERNAL  INTEGUMENT. 

II.  Phenomena  of  exchange  effected  hy  the  sJcin. 

These  exchanges  can  be  effected  either  from  without 
inwards  (absorption),  or  from  within  outwards  (secre- 
tions). 

A.  Absorption. 

Absorption,  by  means  of  the  cutaneous  surface  of  the  skin, 
is  still  a  much  disputed  question.  One  entire  system  (the 
iatraliptic  or  endermic  system)  of  administering  medicaments 
supposes  that  absorption  by  the  skin  does  really  take  place ; 
it  must  be  observed,  however,  that  in  such  cases  the  condi- 
tion of  the  skin  is  changed  either  by  mechanical  action,  such 
as  mercurial  friction,  or  by  chemical  action,  such  as  the  appli- 
cation of  alcoholic  dyes,  rancid  pomades,  etc.  etc.  Colin 
produced  absoi'ption  by  mechanical  action  in  an  experiment 
which  is  often  referred  to,  and  which  consisted  in  causing 
water  impregnated  with  cyanide  of  potassium,  to  drip  for  five 
hours  upon  the  back  of  a  horse ;  the  percussion  thus  pro- 
duced at  length  effected  the  destruction  of  the  sebaceous 
matter,  and  caused  the  cyanide  to  pass  into  the  system 
through  the  skin,  and  the  animal  was  poisoned  by  cutaneous 
absorption.^  The  really  physiological  question  is  reduced  to 
whether  a  healthy  skin  will  absorb  water:  the  ancients  main- 
tained that  it  does,  but  our  present  knowledge  of  the  subject 
seems  to  show  that  this  is  a  mistake.  Setting  aside  the  many 
causes  which  have  given  rise  to  this  error,  it  may  be  proved 
that  no  absorption  takes  place  from  remaining  a  long  time  in 
a  bath :  recently,  at  Vienna,  experiments  have  been  made  of 
long-continued  immersion,  as  a  new  treatment  for  diseases  of 
the  skin,  and  patients  have  remained  immersed  in  a  bath  for 
weeks  and  months,  without  any  sensible  absorption  taking 
place,  the  patients  continuing  to  experience  thirst,  and  being 
obliged  to  swallow  as  much  hquid  as  if  they  had  lived  en- 
tirely in  the  air.  .  The  small  quantity  which  is  occasionally 
absorbed  is  either  introduced  by  the  points  of  transition  be- 
tween the  skin  and  the  mucous,  or  by  the  orifices  of  the 
sudoriparous  and  sebaceous  glands.  It  appears  to  be  a  gen- 
eral law  of  animal,  as  well  as  vegetable  organisms,  that  the 
epidermis  resists  absorption  :  the  vegetable  bark,  or  epidermis 
of  a  fruit,  closely  resembles  the  bark,  or  epidermis  of  an 
animal ;  the  epidermis  of  a  grape  resists  the  phenomena  of 

1  See  G.  Colin,  "  Physiologie  comparee  des  Animaux  Domes- 
tiques."     1873,  Vol.  II.  p.  123. 


THE  SKIN.  371 

interchanges,  and  thus  prevents  the  fruit  from  drying  as  long 
as  it  is  perfect ;  the  slight  dryness  which  appears,  is  effected 
by  means  of  the  pedicle. 

The  structure  of  the  epidermis  is  not,  however,  well 
adapted  for  the  penetration  of  fluids  deposited  upon  its  sur- 
face, and  the  question  arises  how  they  can  pass  through  these 
corneous  layers  covered  as  they  are  with  fatty  matter.  Arti- 
ficial absorption  can  only  be  indirectly  produced:  for  this 
purpose,  fatty  substances  (ointments  or  pomades)  are  em- 
ployed, which  mix  readily  with  the  fatty  matter  of  the 
epidermis ;  if  watery  fluids  are  to  be  introduced,  the  skin  is 
carefully  washed,  and  cleansed  as  thoroughly  as  possible,  and 
yet,  in  spite  of  this  ablution,  scarcely  any  absorption  takes 
place.  That  fatty  bodies  do  not  allow  of  the  absorption  of 
medicines  is  due  to  the  fact  that  these  mingle  with  the  oily 
secretion  of  the  skin;  whilst  the  glyceroles  or  glycerides 
(such  as  plasma,  etc.),  moreover,  are,  perhaps,  even  less 
absorbable  than  water.  That  the  skin  has  any  power  of 
absorption  must  therefore  be  almost  totally  denied.^  If  a 
substance  is  to  penetrate  the  organism  through  the  skin,  it 
must  be  placed  in  the  deep  layers  of  the  epidermis,  the  layer 
of  Malpighi,  and  there  is  no  need  to  go  beyond  this;  for  in- 
stance, in  vaccination,  the  substance  (vaccinal  lymph)  need 
only  be  placed  in  contact  with  those  globular  layers  which 
are  extremely  sensitive  and  impressible :  this  method  is  now 
very  generally  employed,  and  is  called  the  endermic  method, 
though  it  might,  in  some  cases,  be  better  called  the  enepi- 
dermic. 

The  skin  is  permeable  by  gas ;  Bichat's  experiment  is  well 
known,  showing  that  the  cutaneous  surface  of  a  limb,  if  im- 
mersed in  putrid  gases,  absorbs  them  ;  so  that,  being  intro- 
duced into  the  organism,  they  finally  pass  out  through  the 
lower  part  of  the  digestive  tube.  All  kinds  of  miasma  appear 
to  penetrate  the  organism  in  this  way  with  the  greatest  ease. 
The  ready  absorption  of  gas  by  the  skin  has  led  some  authors 

*  And  yet  there  are  experiments  recorded  in  many  standard 
works,  which  have  been  collated  and  criticised  by  Dr.  Stille 
("  Therapeutics  and  Mat.  Med.,"  4th  ed.,  pp.  Gl  et  neq.),  accord- 
ing to  which  it  must  certainly  be  admitted  that  certain  salts  in 
aqueous  solutions,  as  even,  perhaps,  water  itself,  can  be  absorbed 
by  the  cuticular  covering.  Certain  experiments  undertaken  by  the 
Am.  editor  induce  him  to  believe  that  bromide  of  potassium  can  be 
absorbed  by  the  endermic  method.  ( FiVie  "  Bromides  of  Potas- 
sium," by  E.  H.  Clarke  and  R.  Amory.     Boston,  1872.)    [Am.  ed.] 


372 


EXTERNAL  INTEGUMENT. 


to  imagine  that  cutaneous  absorption  takes  place  only  in  the 
case  of  volatile  matters.  Rabuteau  tells  us  that  if  iodine  is 
found  in  the  urine  after  rubbing  with  an  ointment  containing 
an  iodide,  or  after  wearing  a  shirt  dipped  in  iodide  of  potas- 
sium, it  is  because  the  acids  of  the  fats,  which  at  length  tuni 
rancid,  as  well  as  the  acids  of  the  perspiration,  have  set  free 
the  iodine,  which,  from  its  volatility,  is  absorbed  by  the  skin. 

B.  Secretions. 

On  the  other  hand,  the  skin  is  exceedingly  well  adapted 
for  the  purpose  of  secretion^  being  the  seat  of  continual  growth 
and  decay  on  the  part  of  the  globules ;  these  processes  con- 
stitute the  mechanism  of  secretion.  The  furfuraceous  de- 
squamation may  be  considered  as  a  diffuse  secretion ;  the 
phenomenon  of  secretion,  however,  may  be  still  more  clearly 
observed  in  the  sudoriferous  and  the  sebaceous  glands,  of 
whose  action  the  mammary  secretion  is  an  exaggerated  form 
of  result. 


Fig.  96.  —Development  of  the  sudoriferous  glands.* 

The  secretory  organs  are  formed  in  the  ordinary  manner 
from  the  globular  elements  of  the  malpighian  layer  (Fig.  96). 
This  vegetation  sometimes  appears  in  the  form  of  a  tube, 


*  A,  Development  of  the  sudoriferous  glancVs,  in  consequence  of  the  prolif- 
eration inwards  of  cells  of  RIalpighi's  layer,  e,  Epidermis,  r,  Layer  of 
Malpighi.  g.g^  Solid  prolongations  representing  the  beginning  of  the  gland 
(Kolliker).  B,  Portion  of  developed  sudoriferous  canal.  <, «,  Timica  propria, 
e,  e,  Epithelial  layer. 


SWEAT.  373 

which  sinks  to  a  great  depth,  and  passes  through  the  dermis; 
then,  on  reaching  the  adipose  panicle,  being  unable  to  go 
farther,  winds  round  itself,  and  continues  to  grow  until  it 
forms  a  glomerulus ;  this  is  the  coil  of  the  sudoriferous  or 
sweat  gland  (see  Fig.  98).  At  other  times  they  form  larger 
but  less  profound  growths,  terminating  in  short,  rounded  culs- 
de-sac :  these  are  the  sebaceous  glands ;  a  vegetation  resem- 
bling this,  but  on  a  much  larger  scale,  produces  the  secretory- 
elements  of  the  mammary  gland  (Fig.  99  and  100). 

1.  Sudoriferous  or  Sweat  Glands  and  Perspiration. — The 
sweat  glands  are  very  numerous :  it  has  been  estimated  that 
no  fewer  than  from  two  to  three  millions  of  them  are  spread 
over  the  surface  of  the  body.^  They  are  found  almost  every- 
where, the  greater  number  being  in  the  folds  of  the  cutaneous 
surface :  in  the  armpit  they  form  a  sort  of  reddish  continu- 
ous layer;  they  are  not  found  on  the  inner  surface  of  the 
pinna  of  the  ear,  while  in  the  external  auditory  canal  they 
form  a  circle  of  large  glands  placed  close  together  {cerumi- 
notis  glands). 

The  tube  which  forms  these  glands  has  about  the  diameter 
of  a  very  fine  hair :  it  is  at  first  rolled  up  {glomerulus)  in  the 
depth  of  the  dermis ;  then,  becoming  straight  again,  passes 
through  the  dermis  and  continues  as  a  tube,  a  simple  inter- 
cellular lacuna,  which  passes  like  a  corkscrew  through  the 
epidermis  (Figs.  97  and  98).  The  average  total  length  of 
one  of  these  tubes  is  two  millimetres ;  if,  therefore,  all  the 
sudoriferous  tubes  were  placed  end  to  end,  their  total  length 
would  be  four  kilometres:  the  total  mass  of  the  sudoriferous 
system  has,  therefore,  been  estimated  at  half  that  of  the  kid- 
ney, or  a  quarter  of  the  whole  renal  system ;  these  figures 
serve  to  show  the  relative  importance  of  these  two  classes  of 
secretory  glands. 

The  fluid  secreted  by  the  sudoriferous  glands  has  never 
been  collected  in  a  perfectly  pure  state,  because,  in  spreading 
over  the  epidermis  it  mingles  with  other  products  of  this 

*  Sappey  counted  neai-ly  120  orifices  of  sudoriferous  glands  in  a 
square  centimetre  in  parts  of  the  body  where  the  epidermis  is  thin. 
They  are  still  more  numerous  (nearly  300  to  a  square  centimetre) 
in  the  plantar  and  palmar  regions.  Their  total  number,  according 
to  these  calculations,  must  reach  two  millions:  "it  even  exceeds 
this  number,  although,  in  making  this  estimate,  we  have  not  taken 
into  account  the  glands  of  the  arm-pit,  which  are  still  more  numer- 
ous than  those  of  the  hand  or  the  foot,  and  occupy  a  circulating 
surface  of  only  three  or  four  cm.  in  diameter  "  (Sappey). 


374 


EXTERNAL  INTEGUMENT. 


organ.  It  is  also  very  difficult  to  estimate  the  quantity  of 
perspiratioD,  especially  as  it  varies  greatly  under  different 
circumstances :  in  some  cases,  as  much  as  from  1  to  100  times. 
The  average  quantity  of  perspiration  in  24  hours  has,  how- 
ever, been  estimated  at  1  kil.  300  grams.,  containing  from  15 
to  20  grams,  of  solid  matter.  If  the  quantity  of  perspiration 
is  greatly  increased  the  solid  excreta  increase  also,  which 
explains  the  weakness  accompanying  long-continued  perspi- 


Fig.  97.  —Orifices  in  the  su- 
doripaxons  glands.* 


Fig.  98.  —  Vertical  section  of  the  skin,  whose  but- 
face  is  represented  in  the  preceding  figure,  t 


ration.  The  normal  and  solid  product  of  the  sweat  (15  to 
20  grms.)  represents  about  one  quarter  of  the  solid  product 
of  urine  (60  to  70  grms.);  this  relation  is  precisely  the  same 
as  that  which  we  pointed  out  between  the  extent  of  tlie  two 
apparatus;  it  may  be  generally  asserted,  that  the  solid  por- 
tion of  glandular  products  is  in  proportion  to  the  extent  or 
mass  of  the  glands,  and  that  it  is  only  the  amount  of  water 
which  is  variable. 

The  perspiration  or  sweat  is  composed  of  water,  the  ordi- 
nary salts  of  the  blood,  fatty  principles,  and  a  large  number 
of  acids,  such  as  formic,  butyric,  and  propionic  acid,  as  well 


Skin  of  the  hand,  pahnar  region. 


Skin  seen  from  the  upper  surface.    «, 
^  '"        "  c,  Sudori- 


Elevation  formed  by  a  series  of  papilla;.    6,  Interpapillary  fissures, 
parous  pores.    (Gurlt.) 

t  «,  Superficial  layer  of  the  epidermis,  c,  Middle  layer.  J,  Malpighian 
layer.  <',  Papilla.  f\  Dermis,  h,  Adipose  tissue,  i,  Sudori])arous  glands,  with 
their  excretory  tubes  twisted  iu  a  spiral  shape  at  b  and  y.    (Gurlt.) 


SWEAT.  375 

as  an  acid  which  is  peculiar  to  it,  and  is  called  sudoric  acid 
(Favre).  The  reaction  of  the  sweat  is,  therefore,  generally- 
acid,  and  becomes  still  more  so  when  the  fatty  substances 
which  it  contains  are  decomposed,  and  allow  their  acids  to 
be  set  free.  It  is  these  fatty  and  volatile  acids  which  impart 
to  the  blood  its  acid  odor,  which  differs  greatly  in  different 
persons,  and  also  in  different  races  of  men.  The  sweat 
always  contains  a  small  quantity  of  fat ;  thus  there  are  no 
sebaceous  glands  in  the  palm  of  the  hand,  but  numerous 
sudoriferous  glands,  the  product  of  which  always  contains  a 
certain  proportion  of  fatty  matter.  The  perspiration  of  some 
parts  (the  glands  of  the  arm-pity  and  especially  t/ie  cerumi- 
Qious  glands)  contains  a  much  larger  proportion  of  fats.  Finally, 
some  nitrogenous  matters,  urea,  among  others,  are  found  in 
the  perspiration ;  if  the  decomposition  of  these  products  ex- 
ceeds that  of  the  fats,  ammonia  is  produced,  and  the  perspi- 
ration becomes  alkaline.  The  elimination  of  the  urea,  and,  in 
general,  that  of  the  products  of  combustion  of  the  albumi- 
noids is  of  sufScient  importance  to  render  the  skin  an  cmunc- 
tory  similar  to  the  kidney,  and  which  may  supply  its  place  in 
some  cases.  We  shall  find  that,  in  the  normal  state,  two- 
thirds  of  the  nitrogen  introduced  into  the  organism  is 
eliminated  by  the  urine ;  the  other  third  probably  escapes, 
partly  by  the  lung,  with  the  fecal  matters,  or  through  the 
skin. 

The  sudoriferous  secretion  was  formerly  supposed  to  be 
only  the  evaporation  of  the  fluid  parts  of  the  blood  while 
passing  through  the  epidermis.  The  discovery  of  the  sweat 
glands  has  shown  where  this  secretion  is  produced :  in  order 
to  understand  the  interior  mechanism  of  the  secretion  of 
these  glands,  the  ceruminous  glands  must  first  be  studied ; 
we  find  that  their  thick  and  fatty  product,  cerumen^  is  pro- 
duced by  the  imperfect  m,elting  of  the  globules  of  the  gland ; 
the  perspiration  of  the  armpit  also  is  remarkable  for  the  pro- 
portion of  solid  matter,  evidently  arising  from  vegetation  and 
decay  of  the  epithelium.  We  are  thus  led  to  believe  that 
the  secretion  of  ordinary  perspiration  takes  place  in  the  same 
manner,  only  by  means  of  a  far  more  perfect  melting^  and 
borrowing  a  much  larger  quantity  of  water  from  the  blood; 
thus,  when  the  blood  is  unable  to  furnish  a  sufiicient  supply 
of  water,  as  in  cholera,  in  which  disease  the  water  becomes 
extremely  thick,  the  perspiration  itself  becomes  viscous,  and 
is  known  as  the  sticky  sweat  of  cholera  patients. 

This  cellular  moulting,  or  secretion,  is  chiefly  produced  by 


376  EXTERNAL  INTEGUMENT. 

the  influence  of  the  nervous  system,  which  not  only  acta  on 
the  vessels  of  the  skin,  but  also  directly  on  the  glandular 
elements ;  hyperaBinia  of  the  skin  (as  occasioned  by  extreme 
heat),  or  great  tension  of  the  blood  (such  as  is  caused  by  the 
absorption  of  a  large  quantity  of  water),  no  doubt  serve  to 
increase  the  quantity  of  sweat,  but  the  nervous  system  pro- 
duces reflex  secretions  which  are  quite  as  energetic,  and  have 
no  resemblance  to  the  congestion  of  the  blood-vessels  in  the 
skin ;  if  the  blood  does  not  furnish  sufficient  water  for  secre- 
tion, a  gland  borrows  its  fluids  from  the  neighboring  tissues, 
exactly  as  we  have  seen  done  by  the  salivary  glands.  The 
profuse  perspiration  of  death  takes  place  when  the  skin  is  cold 
and  pale ;  the  common  saying  that  certain  emotions  produce 
cold  sweats  is  perfectly  correct.  Indeed,  the  "nervous"  con- 
dition has  the  chief  influence  on  sudation ;  we  perspire  often 
when  some  idea,  such  as  fear,  presents  itself  to  our  minds. 
These  sweats  are  often  confined  to  some  particular  part  of 
the  body,  varying  in  different  persons;  some  very  decided 
reflex  actions  ])ro<luce  abundant  perspiration  round  the  waist, 
or  in  some  part  of  the  fice ;  in  cases  of  hemiplegia  the  sweat 
appears  only  on  one  side  of  the  body;  if  some  drops  of  vine- 
gar be  placed  upon  the  tongue  and  tlie  mucous  tissue  of  the 
mouth,  large  drops  of  perspiration  will  appear  on  the  fore- 
head, or  sometimes  on  one  side  of  the  forehead,  or  of  the  lace. 
The  nervous  organs  for  these  reflex  actions  are  not  yet  per- 
fectly known ;  their  centre  appears  to  be  found  in  the  spinal 
cord. 

The  sweat  thus  secreted  by  the  sudoriferous  coil,  follows 
the  excretory  tube,  until  it  reaches  the  epidermis,  the  differ- 
ent layers  of  which  it  traverses  by  means  of  a  tube  without 
any  proper  walls,  which  is  a  hollow  in  the  midst  of  these 
layers.  As  the  malpighian  layer  contains  a  large  quantity  of 
fluid,  and  the  corneous  layei-,  properly  so-called,  is  very 
coherent,  these  layers  derive  nothing  fi-om  the  perspiration ; 
but  the  most  superfici.-.l  layer,  the  pulverulent  furfuraceous 
or  porous  corneous  layer,  collects  a  large  quantity  in  its  inter- 
stices. The  perspiration,  as  it  reaches  this  point,  resembles 
a  river  lost  in  the  sands;  nearly  all  the  fluid  disappears. 
Thus  if  the  skin  of  a  man  in  good  health  be  touched,  it  la 
found  to  be  slightly  damp,  and  produces  an  indefinable  sensa- 
tion, which  is  lacking  during  that  period  of  a  fever  in  which 
the  perspiration  is  entirely  suppressed.  It  is  only  in  cases 
where  the  perspiration  is  extremely  plentiful  that  it  over- 
flows, after  being  diffused  through  the  pulverulent  layer,  and 


SWEAT.  377 

appears  in  small  drops  in  the  excretory  tubes.  In  general, 
however,  the  perspiration  remains  in  the  furfuraceous  layers, 
and  thus  gives  rise  to  the  moisture  of  the  skin. 

This  humid  condition  of  a  superficial  porous  layer  places 
the  skin  and  the  entire  organism  in  a  peculiar  state :  tl.e  loss 
of  heat,  which  is  in  exact  proportion  to  the  abundance  of  the 
perspiration,  produces  constant  evaporation.  The  human 
body  resembles,  in  this  respect,  those  porous  vases,  or  alca- 
zaras,  which  are  used  to  cool  water  by  means  of  the  evapor- 
ation which  takes  place  on  their  surface:  as  sudation  ifi 
generally  increased  by  the  elevation  of  the  external  temper- 
ature, or  by  any  exertion  (muscular  labor)  which  has  a 
tendency  to  produce  heat  in  the  body,  we  possess  a  moans  oi' 
defence  against  any  too  great  accumulation  of  caloric;  we 
have  seen,  indeed,  in  our  study  of  animal  heat,  that  our  tem- 
perature cannot,  without  danger,  go  beyond  40  or  43  degrees 
(C.)  (see  p.  343).  While,  however,  the  perspiration  forms 
a  valuable  aid  in  resisting  heat,  it  also  renders  us  liable  to  a 
great  danger,  as  any  excess  or  derangement  is  followed  by  a 
chill. 

When  such  a  chill  takes  place,  the  secretion  of  the  perspir- 
ation ceases  suddenly;  this,  however,  usually  happens  too 
late,  and  the  harm  is  done :  these  chills  produce  extremely 
serious  and  varied  effects  on  all  the  parts  of  the  organism. 
In  olden  times  the  arrest  of  sudation  was  looked  upon  as  the 
most  important  part  of  the  whole  process,  and  perspiration 
was  looked  upon  chiefly  as  an  emunctory;  its  suppression 
was  considered  the  retention  of  poisonous  materials.  The 
perspiration,  no  doubt,  contains  excreta,  but  not,  it  would 
seem,  in  sufficient  quantity  to  produce  blood  poisoning,  and 
while  we  consider  the  cooling  effect  as  the  princi})al  physiolog- 
ical office  of  the  perspiration,  we  look  upon  any  exaggeration 
of  it  as  the  chief  cause  of  some  derangements  in  which  the 
suppression  of  the  perspiration  is  only  a  concomitant  phe- 
nomenon. One  of  the  first  effects  that  follow  this  cooling  is 
invariably  a  change  in  the  blood,  the  fibrine  of  which  in- 
creases; this  may  perhaps  be  owing  to  some  derangement 
in  the  condition  of  the  deep  layers  of  the  epidermis,  as,  in- 
deed, in  such  cases,  ganglionic  swellings  are  often  observed, 
the  suffering  or  agony  of  the  epidermis  being,  as  it  were, 
transmitted  to  them  by  means  of  the  lymphatic  vessels.  Dr. 
Lang  (of  Gottingen),  however,  by  studying  the  effects  pro- 
duced from  suppression  of  cutaneous  perspiration,  has  obtained 
the  following  results:   on  making  the  autopsy  of  animals 


378  EXTERNAL  INTEGUMENT. 

which  have  died  after  being  coated  with  a  varnish,  he  found 
peculiar  crystals  of  ammonio-mngnesia  phosphate  in  the  cellu- 
lar tissue,  the  peritoneum,  and  the  muscles.  Study  of  ex- 
periments of  this  kind  seems  to  show  that  when  the  cutaneous 
excretion  is  suppressed,  the  eliminated  products  have  a  ten- 
dency to  pass  through  the  kidney ;  this  organ  is  consequently 
in  a  state  of  hyperaemia ;  later,  an  exudation  takes  place  in 
the  uriniferous  canaliculi,  which  are  finally  obliterated ;  this 
produces  retention  of  the  urea  with  all  the  consequences 
which  belong  to  it.  We  therefore  naturally  suppose  that  this 
substance  being  retained  in  the  blood,  when  decomposed, 
produces  ammonia;  this,  combining  with  the  phosphates, 
gives  rise  to  the  formation  of  the  above-mentioned  crystals  of 
ammonia-magnesia  phosphate.  Researches  made  as  to  cause 
of  death  in  consequence  of  burns  of  a  large  extent  of  surface 
yield  the  same  results.  The  cause  of  death,  following  the 
suppression  of  cutaneous  perspiration,  is  therefore  hyperaemia 
of  the  kidneys,  followed  by  parenchymatous  exudation  in  the 
canaliculi  of  the  kidney,  which  are  at  length  obliterated,  thus 
causing  retention  of  the  excrementitial  substances  of  the 
urine.^ 

2.  Glands  and  sebaceous  Secretions.  —  The  sebaceous 
glands  are  found  in  almost  every  part  of  the  integuments : 
they  are  generally  joined  to  the  hair  (see  Fig.  93),  as  we 
have  already  said,  but  in  parts  where  there  is  no  hair,  they 
are  sometimes  found  alone,  as  on  the  glans  and  the  inner 
surface  of  the  prepuce;  finally,  certain  portions  of  the  in- 
tegument, such  as  the  palm  of  the  hand,  have  neither  hair 
nor  sebaceous  glands  (having  only  sudoriferous  glands).  The 
sebaceous  glands  form,  round  the  hair,  numerous  culs-de-sac, 
which  may  be  looked  upon  as  off-shoots  of  the  pilous  follicle 
(Fig.  93  and  95),  and  surround  the  neck  of  the  hair  some- 
times in  such  numbers  as  to  completely  hide  the  pilous  appa- 
ratus. These  glands  form  the  most  simple  type  of  clustered 
or  racemose  glands:  their  contents  consist  of  epidermal 
globules,  the  outer  ones  being  well-shaped  and  exactly  simi- 
lar to  the  elements  of  the  layer  of  Malpighi ;  as  these  globules, 
however,  approach  the  centre  of  the  glandular  cavity,  they 
become  infiltered  with  fat,  hypertrophied,  and,  finally,  separ- 
ate and  allow  their  contents  to  escape  to  form  a  sort  of  emul- 
sion of  fat  and  albuminous  substances,  which  lUls  the  cavity  of 
the  gland,  and  is  thrown  off;  the  secretion  of  the  sebaceous 

»  See  "  Gaz.  Medic,  de  Strasbourg."     Fevrier,  1873. 


BREASTS  AND  MILK.  379 

glands  forms  in  this  way  the  most  simple  type  of  moultmg 
of  the  globules. 

Two-thirds  of  the  sebaceous  matter  thus  produced  consists 
of  water,  —  the  rest  being  chiefly  fats,  some  extractive  and 
albuminous  substances,  and  some  earthy  salts.  The  fatty 
substances  are  the  most  important  in  a  physiological  point  of 
view.  It  is  owing  to  these  latter  that  the  sebaceous  matter 
possesses  the  property  of  imparting  a  certain  quantity  of 
grease  to  the  hair,  and  of  imparting  an  oily  feeling  to  the 
whole  surface  of  the  epidermis,  thus  increasing  its  impermea- 
bility. Whatever  may  be  the  varieties  in  form  and  arrange- 
ment of  the  sebaceous  glands,  their  use  is  always  the  same; 
the  purpose  of  the  meibomian  glands,  which  are  elongated 
sebaceous  glands  situated  in  the  eyelids,  is  to  anoint  their 
free  edge,  and  thus  prevent  the  product  of  the  lachrymal 
gland  from  overflowing  on  to  the  cheeks. 

We  have  already  seen  that  the  tonsil  (see  p.  230)  may  be 
described  as  a  complex  sebaceous  organ,  developed  from  a 
mucous  gland,  and  connected,  at  its  base,  with  the  lymphoid 
follicles :  this  tonsil  likewise  produces  a  sebaceous  matter  the 
use  of  which  is  not  fully  known. 

It  frequently  happens  that  the  secretory  globules  of  the 
sebaceous  glands  do  not  attain  their  maturity  in  a  regular 
manner;  being  imperfectly  dissolved,  the  sebaceous  matter 
remains  in  the  state  of  desquamated  epithelium,  instead  of 
becoming  an  oil  or  half-liquid  fat ;  it  no  longer  flows  easily, 
and  its  accumulation  in  and  dilatation  of  the  glandular  sac 
produces  sebaceous  cysts  or  wens^  which  grow  sometimes  to  an 
enormous  size.  Large  quantities  of  fotty  substances  are  found 
in  these  cavities,  as  well  as  a  surprising  proportion  of  crystal- 
lized cholesterine.  (In  a  cyst  of  this  sort,  containing  2  kilos, 
of  sebaceous  matter,  15  grms.  of  cholesterine  were  found.) 

3.  Breasts  and  Milk.  —  The  mammary  gland  (Fig.  99) 
consists  of  a  union  of  from  15  to  20  highly  developed  seba- 
ceous glands ;  the  glands  of  the  scrotum  and  of  the  fold  of 
the  groin  sometimes  furnish  a  product  closely  resembling 
milk ;  in  the  areola  of  the  nipple  are  found  immense  seba- 
ceous glands,  called  erratic  lacteal  glands^  which  exactly  fol- 
low the  variations  in  development  of  the  mammary  gland, 
going  through  the  processes  of  atrophy  and  hypertrophy  in 
the  same  manner. 

The  numerous  culs-de-sac  of  the  sebaceous  glands,  which 
culminate  in  lacteal  glands,  unite  to  form  the  15  or  20  tubes 
leading  upwards  to  the  nipple,  where  they  open  into  as  many 


EXTERNAL  INTEGUMENT. 


separate  orifices.  The  structure  of  this  apparatus  is  similar 
to  that  of  glands  in  general :  the  glandular  culs-de-sac  are 
filled  with  cells  resembling  those  of 
the  sebaceous  glands ;  the  epithelial 
covering  of  the  lactiferous  canals 
or  tubes  has,  however,  a  tendency 
to  become  columnar.  In  passing 
through  the  nipple,  these  tubes  trav- 
erse a  sub-cutaneous  connective 
tissue  abounding  in  smooth  muscu- 
lar elements,  either  transverse  or 
circular;  the  contraction  of  these 
muscular  fibres,  which  are  only 
an  exaggeration  of  the  smooth 
muscles  normally  attached  to  the 
dermis,  causes  the  elongation  and 
stiffness,  or,  in  short,  the  erection 
of  the  nipple  (see  p.  364). 

The  secretion  of  milk  is  effected  in  the  same  manner  as 
that  of  the  sebaceous  glands :  by  a  moulting  of  the  globules ; 
at  the  beginning  of  the  secretion,  this  mode  of  production 
may  be  readily  observed,  globules  being  still  found  which, 
after  undergoing  fatty  degeneration,  are  not  entirely  dis- 
solved, and  appear  as  cells  containing  numerous  drops  of  fat : 
these  are  the  globules  of  the  colostrum  (Fig.  100).  The 
colostrum  is  thus  the  result  of  a  secretion  not  yet  firmly 
established,  or  rather  interrupted  by  some  intercurrent  cause, 
such  as  the  return  of  the  catamenia  or  pregnancy  in  a  nurs- 
ing mother.^ 


Fig.  99. — Lobule  of  the  mam- 
mary gland.* 


1  This  opinion  as  to  the  formation  of  milk  by  the  moulting  of 
the  cells  is  not  held  by  all  physiologists.  CI.  Bernard's  theory  is 
as  follows:  "  There  takes  place  a  sort  of  budding  (bourgeonnemeni) 
of  the  superposed  cells,  in  which  the  materials  of  the  milk,  casein, 
butter,  etc.,  are  prepared;  the  coat  of  the  lacteal  cell  is  then  dis- 
solved in  an  alkaline  fluid,  and  milk  is  produced."  Ch.  Robin,  on 
the  contrary,  maintains  that  the  cuU-de-sac  of  the  breast,  which 
are  lined  with  epithelium  during  pregnancy,  and  while  little  or  no 
secretion  is  taking  place,  lose  this  epithelium  as  soon  as  the  secre- 
tion is  estabUshed.  If  this  be  so,  the  special  phenomena  of  secre- 
tion must  take  place  in  the  wall  proper  of  the  culs-de-sac.  Ch. 
Robin  also  explains  the  origin  of  the  globules  of  the  colostrum  by 
looking  upon  them  as  white  globules,  degenerated  or  transformed 
leucocytes.      Whenever  the  leucocytes   (white  globules)   remain 


*  »,  V,  V,  Glandular  vesicles,  forming  by  their  union  a  lobule. 


BREASTS  AND  MILK.  381 

When  secretion  has  actually  begun,  themoultingof  the  glob- 
ules is  complete,  and  it  is  difficult  to  find  in  the  milk  any  trace 
of  its  cellular  origin.  The  quantity  secreted  varies,  but  may  be 
generally  estimated  at  1.300  litre  in  24  hours:  the  quantity 
of  bile  produced  is  about  the  same,  but  the  milk  contains 
more  solid  elements  than  this  latter  fluid,  the  proportion 
being  12  parts  in  100  (while  it  is  only  5  parts  in  100  in  the 


c 


Fig.  100.  —Mammary  gland  daring  lactation.    Milk.* 

bile).  These  12  parts  are  composed  nearly  in  the  following 
manner,  at  least  in  the  case  of  women:  first,  1.5  grm.  of 
various  salts  (in  100  grras.  of  milk),  being  for  the  most  part 
salts  of  the  blood,  and  especially  phosphates  of  lime  and 
potash  (a  little  soda),  and  a  certain  quantity  of  iron;  —  2 
gi-ms.  ofy*a^  or  butter  ^uiargarine,  oleine,  etc.)  ;  this  fat  is  the 
only  physical  element  in  good  milk,  and  appears  under  the 
form  of  small  drops  of  various  size,  which  impart  its  peculiar 
white  appearance  to  the  milk  (emulsion) — 3  grms.  (in  100 
grms.  of  milk)  of  caseine^  an  albuminoid  substance,  which  is 
coagulable,  not  by  heat,  but  by  the  gastric  j  uice,  or  by  pep- 
sine,  as  we  saw  when  studying  digestion.  The  principal 
element  (in  woman's  milk)  is,  finally,  the  sugar  of  milJCy 
which  is  in  the  proportion  of  4  parts  in  100,  or  a  little  more. 

motionless  for  a  considerable  time,  they  pass  into  a  granular  state, 
becoming  three  or  four  times  larger  than  when  in  their  normal  con- 
dition; they  also  absorb  fatty  globules,  more  or  less  considerable 
in  size,  exactly  as  the  epithelial  cells  and  the  leucocytes  of  the 
larynx  and  the  trachea  are  filled,  simply  by  penetration,  with 
granules  of  lamp-black  or  other  dust.  The  globules  of  the  colos- 
trum are  formed  in  a  similar  manner,  but  very  rapidly. 

*  A,  Glandular  lobule  of  tlie  mammary  gland,  with  the  milk  flowing  from 
it.  B,  Milk-globules.  C,  Colo.'^trura.  a,  Cells  with  very  di.stinct  fatty  gran- 
ule3.    6,  The  same,  \vhose  nucleus  has  disappeared.    280  diam.    (Virchow.) 


882  EXTERNAL  INTEGUMENT, 

In  cow's  milk,  on  the  contrary,  the  fats  and  caseine  are  pre- 
dominant: while  mare's  and  ass's  milk  resemble  human 
milk  more  closely. 

The  secretion  of  milk  is  essentially  intermittent,  and  takes 
place  only  under  the  influence  of  special  conditions,  connected 
with  the  function  of  the  genital  organs :  this  function  begins 
in  woman  at  the  period  of  parturition,  producing  first  the 
colostrum,  and,  afterwards,  the  genuine  milk.  During  its 
long  periods  of  repose,  the  gland  becomes  atrophied,  as  it 
were ;  this  is  its  normal  condition  in  young  girls,  in  aged 
women,  and  in  men.  It  develops  in  women  at  the  period  of 
puberty,  but  the  mammary  culs-de-sac  and  their  globular 
epithelium  become  distinct  and  well-defined  only  under  the 
influence  of  pregnancy  and  parturition ;  the  moulting,  which 
produces  the  milk,  is  only  the  last  stage  of  this  hypertrophy. 
Direct  excitation,  under  some  peculiar  circumstances,  may, 
however,  give  rise  to  this  hypertrophy  and  moulting:  young 
unmarried  women,  on  giving  their  breast  to  a  nursing  child, 
have  found  this  gland  develop  and  produce  milk,  under  the 
exciting  influence  of  suction,  and  a  similar  phenomenon  has 
been  known  to  occur  in  the  case  of  men.  Finally,  at  birth, 
both  male  and  female  children,  by  means  of  this  same  rudi- 
mentary gland,  secrete  a  fluid  strongly  resembling  milk,  and 
which,  no  doubt,  has  some  connection  with  the  existence  of 
a  similar  fatty  secretion  {vernix  caseosa)  spread  over  the 
whole  surface  of  the  body. 

These  difl^rent  phenomena,  the  first  especially,  prove  that 
the  mammary  secretion  is  a  reflex  phenomenon,  but  experi- 
mental physiology  has  not  yet  pointed  out  through  what 
nervous  organs  this  action  takes  place :  experiments  on  the 
intercostal  nerves,  and  on  the  branches  of  the  sympathetic 
nerve,  have  yielded  no  results.^  As  might  be  supposed,  the 
food  appears  to  have  great  influence  on  the  production  and  the 
character  of  the  milk.  Finally,  it  has  been  observed  that 
many  medicines  administered  to  the  nurse  reappear  in  the 
milk,  and  this  circumstance  afibrds  an  excellent  though 
indirect  method  of  acting  upon  the  child. 

Messrs.  May  en  sen  and  Bergeret  have,  therefore,  by  a  very 
simple  method  of  analysis,  decided  that  a  single,  very  small 
dose,  of  mercury  or  mercurial  salts  will  be  eliminated  in  a 
great  measure  in  the  lacteal  secretion ;  the  mercurialization 

^  See  CI.  Bernard,  *' Liquides  de  I'Organisme.'*  Vol.  11.  p. 
220. 


BREASTS  AND  MILK.  383 

of  tlie  nurse  of  a  syphilitic  child  is,  therefore,  a  very  con- 
venient treatment.^ 

Milk  forms  the  type  of  a  perfect  aliment  (see  p.  209),  being, 
for  a  considerable  time,  the  only  food  of  the  child ;  the  case 
is  the  same  with  regard  to  the  egg,  which  forms  a  similar 
aliment  for  the  bird.  All  the  elements  necessary  to  nutrition 
have  been  found,  by  analysis,  to  exist  in  milk  (see  Sbove)  as 
well  as  in  the  egg:  salts,  hydrocarbons,  and  albuminoids. 
The  proportions  of  these  various  substances  in  milk  are  not, 
however,  exactly  the  same  as  have  been  generally  supposed 
necessary  to  a  properly  mixed  diet.  It  is  generally  admitted 
(Moleschott,  Voit)  that  an  adult  consumes  320  grms.  of  car- 
bon and  21  grms.  of  nitrogen,  or,  in  other  words,  130  grms. 
of  albuminoid  elements,  and  488  grms.  of  hydrocarbons  and 
fats  (fats  84,  hydrocarbons  404)  ;  it  follows  that,  in  this  case, 
the  normal  proportion,  in  a  mixed  diet,  of  nitrogenous  to 
non-nitrogenous  aliments,  is  1  to  3.7,  wliile  in  milk,  as  well 
as  in  the  Q^^->  the  proportion  is  1  to  3,  or,  even,  1  to  2 :  in 
other  words,  the  quantity  of  albuminates  (nitrogen)  is  nmch 
larger,  and  of  hydrocarbons  (carbon)  much  smaller.  This 
fact  may  be  easily  explained,  by  referring  to  what  we  have 
already  said  (p.  78),  as  to  the  im])ortance  of  the  hydrocarbons, 
in  regard  to  the  production  of  force,  muscular  force  espe- 
cially :  the  adult  draws  his  forces  from  the  combustion  of  non- 
nitrogenous  substances,  the  albuminates  scarcely  serving  for 
this  purpose.  On  the  other  hand,  when  the  organism  is  in 
course  of  development,  the  nitrogenous  substances  are  indis- 
pensable to  the  growth  of  the  different  tissues.  It  is,  there- 
fore, easy  to  see  how  mistaken  is  the  common  practice  of 
condemning  children  to  a  diet  containing  a  large  quantity  of 
starch,  and  scarcely  any  nitrogen.'^  The  differences  in  com- 
position of  the  milk  of  the  different  mammals  (see  above), 
are  probably  connected  with  the  greater  or  smaller  quantity 
of  living  force  which  the  young  animals  possess  at  birth : 
thus  young  calves  and  colts  walk  and  run  almost  imme- 
diately; therefore,  they  must,  at  the  very  first,  produce  a 
considerable  amount  of  force,  and  we  have  seen  that  the  milk 
of  the  cow  and  the  mare  contain  a  large  proportion  of  hydro- 
carbons (fat  in  the  cow,  and  sugar  in  the  mare  and  the*  ass). 
Similar  differences  are  also  observed  in  the  eggs  of  different 
birds. 

*  See  "  Journal  de  I'Anat.,"  de  Ch.  Robin.     Janvier,  1873. 

*  Wundt,  "  Physiologie. "     Trad,  de  A.  Bouchard. 


384  EXTERNAL  INTEGUMENT. 

III.  Nervous  functions  of  the  skin. 

The  skin  also  possesses  extremely  varied  functions,  owing 
to  the  numerous  nerves  terminating  in  it.  We  have  already 
studied  the  centrifugal  nerves  which  innervate  its  smooth 
muscles,  and  cause  their  contraction  under  reflex  influence 
(erection  of  the  nipple,  for  instance),  or  which  terminate  in 
the  glands,  and  give  rise  to  their  secretion,  this  influence 
appearing  especially  in  the  case  of  the  sudoriferous  glands. 

The  skin,  however,  possesses  the  greatest  number  of  cen- 
tripetal or  sensory  nerves.  These  have,  sometimes,  general 
functions  which  it  is  difficult  to  specify,  such,  for  instance,  as 
their  influence  as  centripetal  organs  and  starting-points  to 
the  respiratory  reflex  action  (see  Respiration^  p.  337).  The 
skin  is,  however,  the  chief  seat  of  sensation.  The  epidermis 
of  all  those  parts  of  the  skin  which  are  extremely  sensitive, 
exhibit  special  features  (papillae)  connected  with  this  sensi- 
tiveness. Diseases  of  the  epithelium  have,  therefore,  a  great 
effect  on  the  nervous  system :  we  have  already  studied  the 
derangement  produced  by  the  chill  which  follows  a  too  great 
evaporation  of  sweat ;  these  derangements  are,  perhaps,  often 
only  a  nervous  reaction,  or  reflex  phenomenon,  chiefly  affecting 
tlie  vaso-motors  of  different  organs ;  pathology  is  more  and 
more  tending  to  admit  this,  in  order  to  explain  what  -was 
formerly  dignified  with  the  name  oi  metastases  (see  p.  51J. 

The  study  of  the  sensory  functions  properly  so  called  of 
the  skin,  viz.  feeling  and  touch,  will  serve  better  as  an  intro- 
duction to  that  of  the  organs  of  the  senses,  propen/  uo 
called. 


PART   NINTH. 

OEGANS   OF   TflE   SENSES. 


Our  inteiTial  as  well  as  our  external  surfaces  are  subject 
to  the  influence  of  exterior  agents:  most  of  these,  under  the 
form  of  mechanical,  physical,  or  chemical  excitants,  affect  the 
peripheral  origins  of  the  centripetal  or  sensory  nervous 
system,  and  give  rise  to  nervous  phenomena,  the  greater 
number  of  which  we  have  already  studied  with  that  system. 
Thus  we  know  that  there  are  impressions  which  may  pass 
iinperceived  by  the  cerebral  centre,  of  whicli  we  are  uncon- 
scious^ and  yet  cause  reactions  by  their  reflections  in  the 
medullary  system.  These  impressions  and  their  results 
belong  to  the  system  described  by  Marshall  Hall  under  the 
name  of  excito-motor  system,  and  by  Magendie  under  that 
of  unconscious  sensation  or  sensibility,  and  which  we  have 
studied  under  the  name  of  reflex  phenomena :  such,  for  in- 
stance, is  the  sensation  which  causes  the  saliva  to  be 
secreted ;  and  such  also  are  the  phenomena  which  give  rise 
to  the  pulsations  of  the  heart,  for  we  have  seen  that  this 
organ  contracts  under  the  exciting,  or  rather  excito-reflex, 
influence  of  the  blood  upon  its  walls. 

In  studying  the  nervous  system,  we  have  also  pointed  out 
what  is  understood  by  sensation,  or  sensibility  properly  so 
called  (p.  55).  We  have  seen  that  the  phenomena  of  sensa- 
tion may  be  divided  into  phenomena  of  general  sensibility^ 
comj)rising  the  sensations  which  warn  us,  in  a  vague  (senti- 
ment) or  more  or  less  well-defined  (sensation)  manner,  of  the 
changes  taking  place  in  our  bodies ;  and  of  phenomena  of 
special  sensibility^  which,  occurring  in  special  organs,  inform 
us  by  the  modifications  produced  in  these  of  certain  special 
qualities  of  the  objects  by  which  we  are  surrounded. 

25 


386  ORGANS  OF  THE  SENSES. 

It  raust  not,  however,  be  supposed  that  the  boundary  be- 
tween these  two  classes  of  sensations  is  strictly  defined ;  on 
the  contrary,  a  certain  confusion  exists  between  them,  pro- 
duced by  the  infinite  number  of  transitionary  sensations; 
thu«,  for  instance,  one  impression  will  be  perceived  for  two 
or  three  reflex  phenomena  which  will  pass  unperceived ;  and 
thus  the  stomach,  which  generally  has  little  sensibility, 
sometimes  in  a  physiological  state  becomes  extremely  sensi- 
tive to  the  presence  of  food  or  of  foreign  bodies. 

Now  that  we  know  both  the  character  of  the  phenomena 
of  sensation,  and  the  surfaces  which  form  their  starting-point, 
we  will  take  up  the  study  of  general  and  special  sensations 
experienced  at  each  of  these  surfaces.     , 


I.    GENERAL   SENSATIONS. 

The  general  sensations  are  very  widely  diffused.  Many 
surfaces  give  rise  to  those  kinds  of  sensation  only,  which  give 
no  indication  as  to  the  character  or  qualities  of  the  bodies 
which  make  the  impression  ;  but  show  their  influence  only  by 
impressions  which  it  is  diflicult  to  define,  such  as  pleasure  or 
pain,  or  even  by  effects  which  are  still  less  easily  described, 
and  which  belong  in  a  great  measure  to  the  class  of  reflex 
phenomena,  such  as  tichling,  for  instance. 

The  mucous  surfaces  in  general  yield  only  extremely  vague 
sensations.  The  digestive  mucous  tissue  gives  little  indica- 
tion as  to  the  form,  the  temperature,  and  other  properties  of 
the  bodies  brought  in  contact  with  it,  excepting  only  its 
upper  portion  (the  mouth)  where  it  exhibits  a  special  arrange- 
ment, by  means  of  which  it  becomes  the  seat  of  a  special 
sensation,  and  constitutes  the  organ  of  a  sense  (taste)  which 
we  shall  presently  study.  In  cases  of  fistula  of  the  stomach 
or  intestines,  however,  various  substances  have  been  intro 
duced  into  these  tubes,  and  their  internal  surface  touched 
with  different  excitants,  without  the  patient  experiencing  any 
distinct  percepti<»n,  or  any  sensation  resembling  those  which 
we  shall  examine  under  the  name  oi  touch. 

The  vague  sensation  which  warns  us  of  the  need  of  food 
appears  to  be  a  gastric  sensation :  the  seat  of  hunger  is  sup- 
posed to  be  in  the  upper  part  of  the  digestive  tube;  we  have 
already  seen,  however,  that  this  sensation  is  connected  with 
a  general  feeling  of  discomfort,  and  that  it  is  a  call  from  the 
impoverished  blood  for  nourishment.     The  ground  of  this 


GENERAL  SENSATIONS.  887 

opinion  as  to  the  seat  of  hunger  is,  perhaps,  only  in  our 
knowledge  of  the  fact  that  this  sensation  ceases  when  food  is 
introduced  into  the  stomach.^  The  case  is  the  same  in 
regard  to  thirst:  the  sensation  of  dryness  of  the  throat  is 
caused  by  a  diminution  of  secretion  in  these  parts,  as  well  as 
throughout  the  organism,  in  most  cases  this  dryness  being 
accompanied  by  a  diminution  of  the  sweat  and  urine.  The 
sensations  accompanying  satiety  are  also  purely  general,  being 
sometimes  agreeable  and  sometimes  disagreeable,  and  having, 
properly  speaking,  no  fixed  seat :  indeed,  hunger  and  thirst 
are  sometimes  experienced  in  the  highest  degree,  especially 
in  pathological  cases,  and  in  cases  of  non-absorption,  in  spite 
of  the  ingestion  of  large  quantities  of  food  and  drink. 

The  sensations  belonging  to  the  other  extremity  of  the 
digestive  tract  are  more  distinct :  that,  for  instance,  known 
as  the  desire  for  defecation,  the  seat  of  which  is  not,  however, 
easily  defined.  It  is  generally  supposed  to  be  situated  in  the 
rectum,  but  it  seems  more  likely  to  belong  to  the  intestinal 
tube,  as  shown  by  cases  of  abnormal  anus  (see  p.  278).  This 
sensation  indicates  simply  that  the  rectum  is  ready  to  evac- 
uate the  substances  with  which  it  is  filled.  The  defecation 
which  follows  is  an  entirely  reflex  phenomenon,  which  we 
have  already  studied  at  length.  The  agreeable  sensation 
which  follows  defecation  is  caused  by  the  overcoming  of 
a  difHculty;  in  place  of  this,  however,  in  cases  of  irrita- 
tion of  the  intestine  or  rectum,  a  peculiar  and  painful 
sensation  is  sometimes  experienced,  known  under  the  name 
of  tenesmus^  producing  a  desire  to  throw  off  the  fecal 
matters  even  when  the  intestine  is  completely  empty. 

A  foreign  body  produces  scarcely  any  distinct  sensation 
in  the  mucous  of  the  pulmonary  organs:  its  hardness,  its 
form,  and  its  temperature,  are  felt  very  slightly  if  at  all ;  it, 
however,  ])roduces  a  vague  sensation  of  pain  and  uneasiness, 
and  immediately  causes  a  reflex  action,  giving  rise  to  an  in- 
voluntary cough,  for  the  purpose  of  expelling  the  offending 

1  "  I  have  questioned  a  number  of  soldiers  on  this  point,  choosing 
carefully  those  who  were  ignorant  of  anatomy,  in  order  that  their 
replies  might  not  be  influenced  by  any  involuntary  localizing  of  the 
sensation.  Several  among  them  vaguely  indicated  the  neck  or  the 
chest  as  the  seat  of  hunger,  twenty-three  indicated  the  sternum, 
four  could  not  trace  the  sensation  to  any  particular  spot,  while  two 
only  designated  the  stomach.  These  latter  were  hospital  nurses, 
and  had,  consequently,  a  few  ideas  in  regard  to  anatomy."  Schiif, 
"  Physiologic  de  la  Digestion." 


388  ORGANS  OF  THE  SENSES. 

substance.  The  presence  of  bodies  in  these  organs  is  often 
only  discovered  after  death.  The  pulmonary  surface,  pro- 
perly so-called,  appears  to  be  the  seat  of  agreeable  sensations 
(breathing  pure  air)  as  well  as  disagreeable  ones  (breathing 
vitiated  and  confined  air)  ;  these  are,  however,  in  reality, 
more  widely  diffused,  and,  moreover,  like  hunger  and  thirst, 
are  connected  with  the  need  of  the  entii*e  organism  for  a 
greater  or  less  quantity  of  oxygen. 

The  lung  may  even  be  said  to  be  much  less  sensitive  t  lau 
the  intestine;  we  have  seen  that  the  latter,  in  pathological 
cases,  becomes  extraordinarily  susceptible  to  impressions; 
the  lung,  on  the  contrary,  in  a  similar  case,  gives  no  sign  of 
being  diseased,  unless  the  neighboring  parts  are  affected,  the 
pleura,  for  instance  ( pleuritis) ;  in  general,  however,  the 
maladies  of  the  pulmonary  surface  occasion  little  pain,  and 
only  give  rise  to  a  sensation  of  dyspnoea,  a  vague  feeling  of 
discomfort,  the  seat  of  which  is  so  little  understood  that 
people  commonly  attribute  it  to  the  stomnch. 

The  genito-nrinary  mucous^  that  we  shall  study  later,  most 
usually  presents  only  a  dull  sensation,  always  subjective, 
ordinarily  unlocalized,  and  in  no  wise  informing  us  what 
cause  excites  it.  Properly  speaking,  there  is  no  sensation 
or  sensibility  in  the  kidney,  testicles,  or  ovary.  We  will  an- 
alyze, farther  on,  the  desire  to  urinate ;  we  shall  find  it  wholly 
similar  to  that  for  defecation,  and  shall  see  also  that  it  is  in  no 
less  a  degree  specially  localized,  and  is  composed  of  extrinsic 
sensations,  that  we  never  perceive  in  those  parts  where  they 
are  actually  produced.  The  sexual  desire  may,  on  the  one 
hand,  be  compared  with  the  desire  to  urinate,  and,  on  the 
other,  with  the  desire  to  breathe,  with  that  of  hunger  or  of 
thirst,  for  instance;  it  is  a  general  desire, produced  under  the 
influence  of  a  great  number  of  circumstances,  as  much  inter- 
nal as  external,  and  that  we  localize  in  tlie  sexual  organs^ 
because  we  know  the  phenomena  which  take  place  in  them, 
and  that  are  apt  to  calm  the  desire. 

The  emission  of  spermatic  fluid  is  accompanied  with  an 
agreeable  sensation  that  we  refer  to  the  terminal  portion  of 
the  canal  of  the  urethra,  but  whose  seat  is  but  ill-defined,  being 
situated,  like  that  of  the  desire  to  urinate,  in  the  deeper 
portion  (prostatic  region),  because  individuals  whose  glans 
has  been  amputated  refer  their  venereal  sensations  to  the 
navicular  fossa  of  the  urethra  which  they  no  longer  possess. 

The  womb  has  equally  a  mucous  surface  of  dull,  and 
almost   entirely   reflex,   sensibility,  the  most  important   of 


GENERAL  SENSATIONS.  389 

whose  uses  is  the  expulsion  of  the  foetus;  this  is  also 
accompanied  with  violent  pains,  characterized  always  to 
a  greater  or  less  degree  by  energetic  contractions  of  the 
smooth  muscular  fibres.  The  expulsion  is  followed  by  a 
sentiment  of  a  difficulty  overcome,  as  is  that  of  micturition 
and  defecation,  etc.  The  neck  of  the  womb  does  not  even 
partake,  in  spite  of  numerous  nerves,  of  the  sensibility  to 
pain ;  it  can  only  be  the  point  of  departure  for  certain  reflex 
phenomena  :  thus  it  can  be  cauterized  or  incised  without  pro- 
voking any  sensations ;  cancer  of  this  organ  can  become  pain- 
ful only  by  the  development  of  what  we  have  designated  as 
sympathetic  or  reflex  sensations,  and,  better  still,  as  asso- 
ciated sensations  (p.  57)  which  radiate  towards  the  sacrum, 
the  thighs,  the  abdominal  walls,  etc.  (lumbar  and  sacral 
plexus). 

In  order  to  complete  the  study  of  general  sensations,  we 
must  here  say  a  few  words  as  to  the  sensibility  of  the  various 
tissues  connected  with  the  surfaces,  or  placed  between  them 
in  the  deeper  portion  of  the  organism.  As  might  be  sup- 
posed, the  muscular^  C07i?iective,  bony.,  and  glandular  tissues, 
have  either  very  little  sensibility^  or  none  at  all.  The  muscle 
may  be  cut  or  burned,  without  producing  any  very  painful 
sensation,  while,  if  greatly  distended,  or  strongly  contracted, 
it  becomes  the  seat  of  peculiar  vague  and  painful  sensations, 
such  as  cramps,  which  are  generally  experienced  chiefly  in 
the  smooth  muscles  (intestinal,  uterine,  vesical,  colic,  etc.). 
In  cases  of  inflammation  this  tissue  becomes  extremely 
sensitive,  as  do  also  the  bones,  the  tendons,  the  articulating 
ligaments,  and  the  tissue  of  the  glands  themselves.  This 
pathological  sensibility  is,  no  doubt,  caused  by  the  fact  that 
inflammation,  which  has  a  tendency  to  destroy  the  organs 
(especially  the  muscle),  also  attacks  the  nerves  contained  in 
them;  and  because  the  swelling  which  nearly  always  ac- 
companies this  pathological  process,  distends  the  nerves  of 
the  tissue  itself,  and  those  of  the  adjacent  tissues,  and  thus 
occasions  their  hyperesthesia:  this  is  the  reason  that  the 
glands  are  extremely  sensitive  to  compression,  and  very  pain- 
ful when  swollen. 

The  muscle  appears  to  possess  a  peculiar  sensibility  which 
forms  a  sort  of  transition  from  general  to  special  sensations; 
this  is  what  is  called  the  sense  of  contraction,  the  muscular 
sense,  by  which  we  know  that  we  have  executed  movements. 
What  the  mechanism  and  the  organs  of  this  sensation  may 
be,  is  not  yet  decided  (see,  farther  on,  Paciriian  corpuscles 


390  ORGANS  OF  THE  SENSES. 

of  ttie  niuscles),  but  the  muscular  sense  is  none  the  less  an 
indisputable  frict.^  CI.  Bernard  has  made  it  certain  by  vari- 
ous experiments :  if  all  the  cutaneous  nerves  of  the  limb  of 
an  animal  be  cut,  the  skin  is  rendered  completely  insensitive, 
although  the  animal  still  continues  to  walk  tolerably  well, 
probably  because  the  muscular  sensibility  is  preserved.  If 
the  posterior  roots  (that  is,  all  the  sensory  nerves,  muscular 
and  others)  are  cut,  instead  of  the  cutaneous  branches,  the 
movements  made  by  the  animal  become  much  less  steady. 
In  cases  of  extensive  paralysis  in  man,  when  the  sensory 
branches  of  the  muscles  are  implicated,  the  patient  appears 
to  move  his  limbs  with  difficulty,  and  to  be  able  to  do  so, 
only  when  watching  them  so  as  to  direct  their  movements 
(CI.  Bernard).  Finally,  some  pathological  observations  have 
been  made  in  which  paralysis  of  the  muscular  sense  was  ob- 
served, while  the  sensibility  of  the  skin  remained,  or  vice 
versa  (Landry,  Axenfeld).  This  sensibility,  or  rather  mus- 
cular se7ise,  enables  us  to  judge  of  the /brce  and  extent  of  our 
movements :  we  judge  of  their  force  by  distinguishing  the 
difference  between  different  weights,  raised  one  after  the 
other,  provided  that  the  variation  in  the  weight  of  each  be 
at  least  -^  (Weber) ;  and  it  is  remarkable  that  the  sensibility 
for  lifting  weights  is  much  more  acute  than  for  the  pressure 
produced  by  such  weight  (see  farther  on,  sense  of  touch) ; 
this  proves  once  more  that  the  sensibility  of  the  muscles  is 
entirely  distinct  from  that  of  the  skin. 

The  study  of  the  muscular  sense  is  still,  however,  wrapped 
in  such  obscurity  that  some  authors  (Trousseau)  have  entirely 
denied  its  existence,  while  others  differ  greatly  in  their 
opinions  respecting  it :  thus  Wundt  maintains  that  "  the  seat 
of  the  sensations  of  motion  appears  to  lie,  not  in  the  muscles 
themselves,  but  rather  in  the  motor-nerve  cells  (of  the  ante- 
rior gray  matter  of  the  spinal  axis),  since  we  experience  not 
only  the  sensation  of  a  movement  performed,  but  also  that 
of  one  which  has  been  only  intended :  the  sensation  of  move- 
ment thus  appears  to  be  directly  connected  with  motor  inner- 
vation "  (for  which  reason  Wundt  designates  it  as  the  sensation 


1  See  Duchenne  (de  Boulogne),  "  De  rElectrisation  Localisee," 
p.  389.     Paris,  1872. 

CI.  Bernard,  "  Lemons  sur  la  Physiologie  et  la  Pathologie  du 
Syst.  Nerveux."     Vol.  I.  p.  246. 

Jaccoud,  "  Les  Paraplegies  et  I'Ataxie  du  Mouvement."  Paris, 
183  L 


SPECIAL  SENSATIONS.  891 

of  innervatioii)}  It  is,  however,  probable  that  this  sensa- 
tion, by  means  of  which  we  are  made  aware  of  the  degree  of 
contraction  of  our  muscles  {sense  of  muscular  actimty^  Gertly) 
is  the  same  as  that  which  causes  the  sensation  of  fatigue 
which  follows  moderate  but  long-continued  exercise,  and 
that  its  seat  lies  in  the  contracted  fibres,  while  the  sensation 
of  fatigue  experienced  after  violent  exertion  appears  to  reside 
principally  in  the  tendons  (Sappey). 


II.    SPECIAL  SENSATIONS. 

The  special  sensations  render  us  conscious  of  external 
bodies,  and  of  their  various  properties.  They  are  furnished 
by  the  organs  of  the  senses,  each  of  which  supposes,  1,  an 
organ  susceptible  to  the  impression ;  2,  a  nerve,  by  means  of 
which  the  impression  is  transmitted  ;  and  3,  a  central  part  of 
the  brain  by  which  the  impression  is  received  and  under- 
stood. 

The  peripheral  organ,  which  first  receives  the  impression, 
proceeds  always  from  a  more  or  less  modified  part  of  the 
cutaneous  and  external  surface  (epidermis),  or  of  the  most 
primitive  parts  of  the  internal  surface  (epithelium) :  thus  we 
have,  as  oi'gans  of  the  senses  proceeding  from  the  skin,  the 

^  See  also  researches  by  Bernhardt  (Zur  Lehre  von  Muskelsinn. 
Analyse,  en  "  Revue  des  Sciences  Medicales,"  de  G.  Hayem.  Vol. 
I.  p.  61,  1873).  This  author  holds,  with  J.  Miiller,  Ludwig,  and 
Bernstein,  that  the  muscular  sense  simply  consists  in  the  faculty  of 
exactly  estimating  the  intensity  of  the  excitation  which,  beginning 
in  the  encephalon,  results  in  the  movement  intended.  He  found, 
after  causing  the  contraction  of  the  muscles  by  faradization  (the 
interrupted  current)  that  the  person  experimented  upon  experienced 
much  greater  ditficulty  in  recognizing  the  variation  between  differ- 
ent weights  than  when  the  contraction  was  produced  by  the  influ- 
ence of  the  will.  From  this  Bernhardt  concluded  that  the  sense 
of  force  is  'A  psychical  function^  He  admits,  however,  that  the  sen- 
sory impressions  beginning  in  the  soft  parts  adjacent  to  the  muscles 
have  a  powerful  influence  in  completing  the  notion  or  idea  formed 
by  the  centres  of  volition.  According  to  him,  therefore,  the  mus- 
cular sense,  properly  so  called,  has  no  existence.  Trousseau,  con- 
sidering the  subject  from  a  similar  point  of  view,  has  also  denied 
the  existence  of  the  muscular  sense,  referring  every  thing  to  the 
sensibility  of  the  soft  parts  displaced  by  the  movement.  See  Art. 
Ataxic,  en  "  Nouv.  Diet,  de  Med.  et  de  Chir.  Prat'."  VdI.  HI. 
p.  770.) 


392  ORGANS  OF  THE  SENSES. 

organs  of  touch,  sight,  and  hearing ;  and,  from  the  initial 
parts  of  the  digestive  and  the  respiratory  mucous  surface,  we 
have  the  organs  of  taste  and  smeU, 

I.   Feeling  and  Touch. 

This  is  a  mixed  sense,  for  it  enables  us  to  recognize,  1,  the 
pressure  exercised  by  different  bodies  upon  the  integuments, 
and,  2,  the  temperature  of  these  bodies. 

The  organ  of  touch  includes  the  whole  external  integu- 
ment and  a  part  of  the  mucous  surface,  especially  of  the 
primce  vice,  the  mucous  surface  of  the  alimentary  canal  (the 
tongue  and  also  the  teeth).  These  organs  are  formed  of  two 
parts  essential  to  every  integument,  the  epidermis  or  epithe- 
lium, and  the  dermis  ;  the  epithelial  covering,  indeed,  is  in- 
dispensable to  touch,  and  if  its  globular  elements  are  injured 
or  destroyed,  the  sense  of  touch  ceases  simultaneously.  By 
means  of  its  growth  towards  the  exterior,  the  epidermis  forms 
crests,  or  hollow  papillge,  into  wliieh  the  dermis  penetrates, 
bringing  with  it  the  vessels  and  the  nerves;  w^e  are  still, 
however,  unable  to  explain  exactly  this  indispensability  of 
the  epidermis,  since  the  nerves  appear  to  terminate  in  the 
dermis,  and  their  connection  with  the  epithelial  globules  are 
still  hypothetical;  although  it  has  been  demonstrated  in  the 
case  of  certain  organs  (as  we  shall  see  in  regard  to  the  nasal 
chambers  and  the  internal  ear) ;  it  is,  however,  certain  that 
the  more  delicately  formed,  and  highly  developed  is  the 
covering  of  the  papilla3,  the  more  exquisite  is  the  sensibility 
of  the  papillas.  Some  important  growths  of  the  epidermis 
even  appear  to  be  essentially  connected  with  the  exercise  of 
the  sensation  of  touch  :  the  teeth,  which  are  extremely  hard, 
and  covered  with  a  thick  layer  of  modified  epithelium  (the 
enamel),  are  nevertheless  the  seat  of  the  most  delicate  sense 
of  feeling ;  cats  feel  with  the  long  hairs  growing  from  their 
mouth  (see  p.  431 :  tactile  hair) ;  insects  have  horny  feelers; 
the  sole  ot*  the  foot  is  covered  with  a  thick  layer  of  corneous 
epidermis,  and  yet  its  sensibility  is  exquisite.  The  thickness 
of  the  epidermis  is,  therefore,  no  obstacle  to  the  sensibility  of 
the  skin. 

The  papillae  of  the  dermis  contain  the  terminations  of  the 
nerves;  the  papillae  do  not,  however,  all  contain  nervous 
elements,  many  of  them  having  only  vascular  network  (Fig. 
101,  B,  C,  D) ;  the  papillae  of  the  dermis  are  more  highly 
developed  in  proportion  to  the  exquisite  sensibility  of  the 


FEELING  AND   TOUCH. 


393 


part;  in  the  tongue,  for  instance,  they  have  a  finger-like 
formation,  or  exliibit  numerous  divisions.  It  was  formerly 
supposed  that  the  nerves  in  them  terminate  in  loops ;  but 
now  that  small  terminal  organs,  especially  adapted  for  the 
purpose,  have  been  discovered,  this  latter  view  is  being 
gradually  adopted ;  and  indeed  these  tactile  organs  are  being 
constantly  met  with  in  parts  where  their  presence  was  not  in 
the  least  suspected.  Ti»ese  terminal  organs  are  small  ovoid 
bodies,  or  tactile  corjncscles  (of  Meissner  and  Wagner),  gen- 
erally of  the  shape  of  a  pineapple,  or  of  some  simpler  and  less 
regularly  formed  sliape  (corpuscles  of  Ifrai/se),  at  the  base 
of  which  we  find  from  1  to  4  nerve  filaments  which  pene- 
trate, and  appear  to  be  lost  in  the  substance  of  the  cor- 
puscle (Fig.  101,  A).     If  these  nerve  threads  are  cut,  the 


Bensibility  of  the  papillae  containing  the  corresponding  ter- 
minal organs  ceases,  and  these  organs  change  into  a  small 
mass  of  fat ;  in  persons  whose  sensibility  is  paralyzed,  only 
small  drops  of  fat  are  found  in  the  place  of  these  organs; 


*  The  epidermis  and  Malpighi's  network  have  been  removed.  A,  Nervous 
papilla,  with  a  tactile  corpuscle,  into  which  enter  two  primitive  nerve  fibres,  n  ; 
at  the  base  of  the  papilla  are  seen  fine  elastic  nets,  e,  from  which  proceed  fine 
fibres ;  between  and  in  the  midst  of  the  latter  are  seen  corpuscles  of  the  connec- 
tive tissue.  B,  C,  D,  Vascular  papillae,  simple  at  C,  with  loops  formed  b^ 
anastomoses  of  vessels  in  B  and  D.  Near  these  vessels  are  seen  fine  elastic 
fibres  and  corpuscles  of  the  connective  tissue.  /?,  Papillary  body,  havini?  a 
horizontal  direction,  e,  Stellate  elements  of  the  corium.  300  dUam.  (Vir- 
chow.) 


ORGANS  OF  THE  SENSES. 


from  these  facts  the  tactile  bodies,  etc.,  would  seem  to  be  the 
seat  of  sensibility. 

We  also  find  larger  corpuscles  in  the  sub-cutaneous  connec- 
tive ti^ue  and  deep  in  the  dermis,  hanging  from  the  nerve 
tubes  like  fruit  from  the  twigs  of  a  tree, 
and  visible  to  the  naked  eye.  These 
are  the  corpuscles  of  Pacini:  they 
are  surrounded  by  several  fibrous 
envelopes  (Fig.  102),  and  have  an 
elongated  cavity  in  which  one  or 
several  nerve  filaments  terminate  in 
a  manner  not  yet  perfectly  under- 
stood. They  are  found  chiefly  in  the 
palm  of  the  hand,  in  the  path  of  the 
collateral  nerves  of  the  fingers;  their 
presence  in  various  other  organs, 
however,  especially  in  the  mesentery 
of  the  cat,  leads  us  to  doubt  their 
value  as  organs  of  tactile  sensi- 
bility. 

Kolliker  has  attempted  to  prove 
that  these  various  corpuscles  all  be- 
long to  the  same  type,  being  com- 
posed of  similar  essential  parts, 
namely,  1,  terminal  nerve  fibres  (one 
or  several  pale  tubes),  one  end  of 
w^hich  is  always  free,  and  often  en- 
larged in  the  shape  of  a  club ;  2,  an 
internal  bulb  or  central  mass,  formed 
of  a  kind  of  connective  tissue,  and 
serving  as  a  support  or  envelope  of 
the   nerve   fibre;    3,  an    enveloping 

Fig.  102.  —  Pacini's  or  Vater's    i^+i       i'  I-        +• 

corpuscle,  taken  from  the  sheatli  ot  Connective  tissue. 

thi^iirers*'^^*^^*^^^"^^^^     Rouget  is  vcij  justly  opposcd  to 

this  idea  of  the  assimilation  of  the 

various  corpuscles ;  his  histological  researches  have  convinced 

him,  1,  that  there  is  no  real  analogy  between  the  structure 

of  the  tactile  corpuscles  (and  the  corpuscles  of  Krause).,  with 


*  Primitive  nerve  fibre,  containing  medullary  substance,  w,  having  a  marked 
outline,  and  a  thick  nerve  sheath,  /?,/>,  which  contains  longitudinal  nuclei,  and 
forms  the  tail  of  the  corpuscle.  C,  The  corpuscle  proper,  with  its  concentric 
layers  formed  by  the  envelope  of  the  nerve  swollen  into  the  shape  of  a  club,  and 
having  a  central  cavity,  into  which  the  axis-cylinder  passes  and  is  terminated. 
150  diam.    (Virchow.) 


FEELING  AND   TOUCH.  395 

the  Pacinian  corpuscles ;  2,  that  the  tactile  corpuscles  and 
those  of  Krause  are  only  secondary  forms  of  the  same  type ; 
and,  finally,  that  this  type,  in  opposition  to  that  of  the  Pacin- 
ian corpuscles,  j^resents  the  closest  analogy  to  the  funda- 
mental structure  of  the  termination  of  the  motor  nerves. 

The  form  of  the  corpuscles  of  Krause,  as  observed  in  the 
conjunctiva,  appears  to  be  that  of  the  most  elementary  of  the 
nerve  terminations :  it  consists  of  a  nerve  tube,  with  a  double 
outline,  rolled  up  at  its  terminal  portion,  and  deprived  of  its 
medullary  layer,  swelling  out  as  it  loses  itself  in  a  mass  of 
nerve  substance,  exactly  similar  to  that  of  the  axis-cylinder, 
containing  central  nerve  cells ;  this  tube  is  furnished  with 
nuclei,  and  has  as  a  covering  only  the  prolongation  of  the 
sheath  of  Schwann.  The  same  type  is  found  in  Meissner's 
or  the  tactile  corpuscles :  round  the  central  portion  the  nerve 
fibres  are  rolled  up,  with  no  interstices  between  them,  and 
transversely  strewn  with  elongated  nuclei,  and  thus  the  cor- 
puscle gets  that  peculiar  appearance  which  has  been  likened 
to  that  of  a  pineapple,  but  which,  according  to  Rouget,  re- 
sembles much  more  an  ovoid  and  cylindrical  ball  of  twine : 
"  errors  in  observation  have  led  to  the  belief  that  the  nerve 
tubes  terminate  either  in  loose  ends,  or  loops,  on  the  surface 
of  the  corpuscles.  Beginning  at  the  base  of  the  papillae,  the 
nerve  tubes  emanating  from  the  sub-cutaneous  network  turn 
towards  the  axis  and  join  the  tactile  corpuscle,  either  at  its 
lower  extremity  or  at  its  middle  portion ;  sometimes  passing 
along  the  borders  or  the  surface,  they  extend  nearly  to  its 
lower  portion  :  if  the  place  at  which  the  tube  with  the  double 
outline  appears  to  cease  be  carefully  observed,  we  find  that, 
losing  here  its  medullary  layer,  and  the  peculiar  refraction 
belonging  to  it,  the  gray,  pale  nerve  fibre  glides  into  the 
interstice  between  the  transverse  strioB  of  the  corpuscle,  and 
disappears  more  or  less  suddenly  from  sight,  penetrating 
the  interior  of  the  cortical  layers.  In  the  central  mass  of  the 
corpuscle,  the  gray  fibres  with  nuclei  are  not  found,  nor  the 
tubes  with  a  medullary  layer:  this  central  mass  is  composed 
of  a  finely  granulated  and  extremely  refracting  substnnce, 
furnished  with  nuclei,  and  exactly  similar  to  that  which  forms 
the  nerve  off-shoots  of  the  conjunctiva.  ...  It  is  extremely 
probable  that,  as  in  the  case  of  the  ganglionic  corpuscles, 
the  terminal  plates,  the  terminal  end  of  the  electric  plates, 
etc.,  this  is  only  a  swelling  or  opening  out  of  the  peculiar 
nerve  element,  the  axis-cylinder^'' 

The  short,  gray,  horizontal,  and  ribbon-like  fibres,  twisted 


396  ORGANS  OF  THE  SENSES. 

round  a  central  mass  of  nerves,  form  the  elements  which  take 
the  place  of  the  three  portions  of  which  the  tactile  corpuscles 
of  feeling  were  formerly  supposed  to  consist.  The  transverse 
nuclei  belong  to  the  sheath  of  Schwann. 

On  the  other  hand,  the  corpuscles  of  Pacini  and  Vater  are 
found  in  parts  of  the  organism  in  which  they  can  be  of  little 
use  in  respect  to  touch,  properly  so  called  :  we  find  them,  not 
only  in  the  mesentery  (see  above),  but  also  in  the  nerves 
which  go  to  the  bones,  and  even  in  the  interior  of  the 
muscles.  They  appear  to  be  extremely  sensitive  to  compres- 
sion, and  their  function  is,  no  doubt,  connected  with  this 
mode  of  sensibility :  for  instance,  their  sensations  indicate  the 
degree  of  contraction  of  the  muscles,  according  to  the  com- 
pression which  these  muscles  produce  upon  them.  They  are 
also  subjected  to  other  kinds  of  pressure:  thus  the  corpuscles 
situated  in  the  articulating  capsules  are  compressed  by  the 
bones  in  certain  movements,  and  also  by  the  tension  of 
the  ligaments ;  in  the  mesentery,  they  are  compressed  by  the 
abdominal  muscles,  acting  upon  the  walls  of  the  viscera; 
their  superficial  position,  under  the  integuments,  is  favorable 
to  the  transmission  of  external  pressure  (Rauber).^ 

The  functions  of  touch  are  most  highly  developed  in  those 
parts  which  contain  the  largest  number  of  nerves  and  tactile 
corpuscles:  thus  the  organs  which  we  chiefiy  use  are  the 
hands,  the  tongue,  and  the  teeth,  not  forgetting  the  sole  of 
the  feet,  which  is  a  constant  organ  of  touch  during  walking, 
and  which,  judging  of  the  character  of  the  ground,  causes 
and  modifies  the  reflex  action  of  locomotion,  almost  without 
any  exercise  of  the  consciousness  or  of  the  will  (see  p.  48). 
The  parts  in  which  the  sensation  of  pressure  and  of  temper- 
ature reside  are  not  exactly  the  same,  although  it  is  impos- 
sible to  point  out  the  cause  of  this  difference. 

The  sensation  of  temperature  is  abnost  generally  diffused 
over  the  whole  surface  of  the  body,  and  it  would  seem  at  first 
thought  as  if  no  part  is  more  privileged  in  this  respect  than 

*  The  sensation  and  the  measure  of  contraction  of  those  muscles 
in  which  these  corpuscles  are  not  found  is  produced  by  other  special 
methods  of  arrangement.  This  is  the  case  in  regard  to  the  muscles 
of  the  jaw,  and  the  teeth,  the  muscles  of  the  eyelids,  the  conjunc- 
tiva, etc.  A  fact  which  seems  to  show  the  independence  of  the 
muscular  sensations  on  ihe  sensibility  of  the  skin  is,  that  if  this 
sensibility  is  diminished  by  means  of  cold,  the  sensations  of  mus- 
cular contraction  continue  or  are  even  increased.  (Rauber,  Dis- 
sert., Munich,  1805.     See  above,  pp.  389  and  390.) 


FEELING  AND  TOUCH.  397 

another ;  it  is,  however,  commonly  observed  that  the  heat  of 
the  body  is  best  judged  of  by  the  lips,  the  cheeks,  and  the 
back  of  the  hand  :  a  physician,who  desires  to  ascertain  the  tem- 
perature of  a  patient's  skin,  tries  it  with  the  back,  not  the 
palm  of  the  hand  ;  for  the  same  reason,  if  we  wish  to  discover 
if  some  imperceptible  drops  of  rain  are  falling,  we  put  out  the 
back,  not  the  palm  of  the  hand.  This  sense  of  temperature 
acts  only  through  comparison  ;  it  does  not  indicate  the  tem- 
perature of  the  skin,  but  only  the  rise  or  fall  of  the  temper- 
ature; for  instance,  we  are  conscious  of  the  difference  in 
temperature  between  our  hand  and  forehead  only  at  the 
moment  when  we  touch  the  forehead  with  the  hand. 

In  order  to  bring  this  thermal  sensibility  into  play,  the 
temperature  to  be  ascertained  must  be  between  0^  and  70® 
(C.) ;  outside  of  these  extremes  only  painful  sensations  of 
cold  or  heat  are  felt,  and  we  are  unable  to  judge  of  the 
difference  of  a  few  degrees:  we  judge  best  of  a  slight  varia- 
tion in  the  temperature  of  a  body  when  between  SO'*  and  50° 
(C.)  ;  in  other  words,  the  temperature  is  more  easily  ascer- 
tained the  nearer  it  approaches  that  of  our  own  body,  and 
also  if  a  considerable  part  of  its  surface  be  compared  at  the 
same  time ;  thus  a  finger  dipped  into  a  fluid  at  37°  (C),  gives 
an  idea  of  less  heat  than  an  entire  hand  in  one  at  only  30° 
(C).  Anaemia  appears  to  increase  the  sensibility  of  the  skin 
to  differences  of  temperature,  while  hyperaemia  diminishes  it. 

The  sensation  of  pressure,  produced  in  us  by  different 
bodies,  is  very  unequ.dly  distributed  in  different  parts :  it  is 
most  acute  at  the  tip  of  the  tongue  and  the  ends  of  the 
fingers:  thus  the  digital  extremities  are  points  in  which  our 
sense  of  touch  chiefly  lies.  In  order  to  decide  exactly  the 
degree  of  sensitiveness  of  different  parts  of  the  body,  a  pair 
of  dividers  is  employed  (Weber's  compass),^  and  the  degree 
of  sensibility  of  the  surface  is  measured  by  the  distance  that 
one  leg  of  the  dividers  is  from  the  other,  when  a  person  can 
perceive  the  impression  of  the  two  points  of  contact ;  the  less 
the  distance  between  them,  the  greater  the  amount  of  sensi- 
bility. At  the  tip  of  the  tongue  1  m.m.  of  distance  is  sufli- 
cient ;  2  m.m.  on  the  palm ;  and  12  m.m.  on  the  back  of  the 
hand :  while  on  the  skin  of  the  trunk,  especially  in  the  dorsal 
region,  the  distance  must  be  5  or  6  Centimetres. 

While  applying  the  name  of  circle  of  sensation  to  that  ex- 

1  See  Weber,  Art.  "  Tastsina "  in  "Wagner's  Handworter- 
buch  der  Physiologie." 


398  ORGANS  OF  THE  SENSES. 

tent  of  the  surface  of  the  skin  in  which  the  impression  made 
by  the  two  points  of  the  dividers  (aesthesiometer)  forms  only 
one,  we  find  that  the  extent  of  these  circles  differs  greatly 
according  to  the  parts  of  the  body  under  consideration;  the 
limit  is  very  small  at  the  tip  of  the  tongue,  but  increases 
greatly  in  the  dorsal  regions  of  the  trunk;  anatomical  data 
also  show  that  this  extent  is  in  inverse  ratio  to  the  quantity 
of  tactile  corpuscles  contained  in  the  skin.  We  must  not, 
however,  decide  absolutely  from  this  that  a  circle  of  sensa- 
tion has  an  anatomical  breadth  or  size,  such,  for  instance,  as 
the  space  enclosed  by  the  ramifications  of  a  nerve  fibre :  in 
order  to  prove  the  contrary,  it  is  sufficient  to  remember  that 
the  extent  of  a  circle  of  sensation  varies  according  to  atten- 
ti'on,  exercise,  habit,  and  other  influences.  Since  the  space 
which  is  between  the  points  of  the  dividers,  in  certain  parts, 
contains  more  than  twelve  ofKrause's  corpuscles, while  in  these 
parts  two  circles  of  sensations  meet,  or  even  partly  overlap 
each  other,  so  that  they  cannot  be  separated  by  perception  ; 
we  must  admit  that  these  are  phenomena  of  radiation,  that 
is  to  say,  that  the  excitation  of  sensory  nerve  fibre  is  trans- 
mitted toother  adjacent  fibres;  and  since  attention,  habit, 
and  exercise  can  diminish  this  radiation,  we  must  conclude 
that  it  is  not  an  instance  of  peripheral  impression,  but  of 
central  perception. 

In  regard  to  the  skin  of  the  various  segments  of  the  limbs, 
especially  of  the  arm,  Vierordt  has  arrived,  by  means  of 
numerous  and  careful  experiments,  at  the  conclusion  that  the 
sensibility  (sense  of  touch  or  sense  of  localization)  varies  in 
proportion  to  the  distance  between  the  point  considered  and 
the  articulation  immediately  above  it,  going  back  as  for  as  to 
the  root  of  the  limb.  The  comparative  values  of  the  delicacy 
of  the  sense  of  localization  also  form  the  sum  of  two  breadths : 
the  one,  which  is  constant,  being  the  sensibility  of  the  skin 
in  the  axis  of  the  articulation ;  the  other,  which  is  variable, 
being  in  proportion  to  the  distance  between  the  point  under 
consideration  and  the  articulation  situated  below  it,  and, 
therefore,  in  proportion  to  the  extent  of  the  movements  of 
localization  around  the  articulation. 

One  remarkable  circumstance,  which  may  be  easily  ex- 
plained by  referring  to  our  study  of  the  nervous  system  is, 
that  prolonged  sensations  of  pressure  last  for  a  considerable 
time  after  the  causes  producing  them  have  ceased  to  act: 
persons  who  wear  spectacles  feel  them  still  after  taking  them 
off;  and  after  holding  an  object  in  the  liand,  we  sometimes 


FEELING  AND  TOUCH.  399 

seem  to  feel  it  long  after  we  have  let  it  go.  This  is  a  kind 
of  echo  of  sensation,  and  is  purely  subjective. 

The  manner  and  form  in  which  the  sensation  of  pressure 
is  produced  by  different  bodies  give  us  such  exact  informa- 
tion as  to  their  nature,  that  we  might,  without  close  examina- 
tion, suppose  this  to  be  the  result  of  special  sensations.  Thus, 
we  judge  if  the  surface  of  a  body  is  smooth  or  rough,  if  it 
exhibits  any  anfractuosity  (peculiar  conformations),  by  the 
way  in  which  it  presses  upon  our  digital  extremities ;  by 
passing  our  fingers  over  surfaces  we  judge  of  their  form.  Tho 
variations  of  pressure,  and  the  reactions  of  a  body  in  opposi- 
tion to  efforts  which  we  ourselves  make,  enable  us  to  judge 
whether  it  is  hard  or  soft:  we  judge  in  the  same  way  whether 
it  is  in  large  pieces  or  dust ;  whether  it  is  solid  or  liquid :  in 
short,  we  obtain  precise  ideas  as  to  the  condition,  the  form, 
and  extent  of  the  body. 

Differences  of  pressure  also  enable  us  to  judge  of  the  weight 
of  a  body ;  but  it  must  be  admitted  that  the  muscular  force 
necessary  to  counterbalance  the  weight  (see  p.  453)  is  of 
chief  importance  in  our  estimate. 

Finally,  the  sensations  of  pressure,  form,  weight,  and  tem- 
perature, are  often  connected  with  each  other ;  thus,  of  two 
equal  weights,  the  colder  will  seem  the  heavier ;  if  we  place 
upon  our  forehead  two  five-franc  pieces  of  different  temper- 
ature, the  warmer  will  appear  to  be  the  lighter.  On  the 
other  hand,  smooth  bodies  appear  to  be  colder  than  those  of 
uneven  surface,  and,  subjectively,  they  really  are  so,  because, 
their  surfaces  being  unbroken,  more  caloric  is  drawn  from  us. 

The  most  striking  example  of  the  perfection  to  which  the 
sense  of  touch  may  be  brought,  is  found  in  the  case  of  blind 
persons,  who  learn  to  distinguish  colors  by  touch ;  as  they 
do  this  solely  by  means  of  the  different  degrees  of  roughness, 
they  are  unable  to  distinguish  natural  colors  whose  surface 
is  equally  smooth. 

Finally,  the  sensations,  whether  general  or  special,  pro- 
duced by  the  skin,  are  reduced  to  three :  contact  (or  pres- 
sure), temperature,  and  pain.  The  nature  of  these  three 
kinds  of  sensations,  and  the  manner  in  which  they  are  pro- 
duced, are  as  yet  undecided ;  as  loss  of  sensation  to  one  may 
exist,  while  sensation  to  the  others  remains  intact,  we  are  led 
to  suppose  that  a  separate  class  of  nerve  fibres  belongs  to 
each,  and  that  pain,  for  instance,  has  not  the  same  path  of 
conduction  as  sensations  of  touch,  while  the  latter  follow 
other  conductors  than  those  of  the  sensations  of  temperature. 


400  ORGANS  OF  THE  SENSES. 

"We  have  already  seen  that  Brown-Sequavd  (p.  46),  allows 
that  those  isolated  conductors  are  found  in  the  spinal  axis, 
and  that  he  estimates  their  number  as  four,  belonging  to  tem- 
perature, pain,  touch,  and  tickling  (mention  is  made  of  the 
muscular  sense,  which  is  entirely  distinct  from  these,  its  con- 
ductors being  found  in  other  strands  of  the  axis). 

The  difference  in  sensations  may,  however,  be  simply  owing 
to  the  specific  energy  of  the  terminal  nei've  organs,  some  of 
which  (corpuscles  of  Pacini)  govern  the  sensations  of  pres- 
sure, and  others  (tactile  corpuscles),  those  of  touch,  or  what 
is  called  the  sensation  for  localization  in  the  skin ;  while 
others  (still  more  difficult  to  define)  regulate  the  sensations 
of  temperature  and  pain.  If  this  be  the  case,  a  special  ex- 
citant will  produce  the  corresponding  special  sensation  only 
when  applied  to  these  nerve  terminations,  and  not  when  it 
reaches  the  trunk  of  the  nerve,  the  fibres  of  which  form  simi- 
lar conductors.  Thus  if  the  elbow  is  dipped  into  cold  water, 
the  ulnar  nerve,  excited  by  this  change  of  temperature,  will 
occasion  sensations  extending  to  the  inner  side  of  the 
hand  (see  p.  56) ;  the  sensation  experienced  in  this  case,  in 
the  little  finger,  consists  of  a  vague  and  undefined  feeling  of 
pain,  not  of  cold,  which  would  be  the  case  if  the  hand  were 
dipped  in  cold  water. 

According  to  some  auth ore,  these  sensations  are  only  higher 
or  lower  degrees  of  an  excitation  the  nature  of  which  is 
always  the  same;  looked  at  in  this  light,  pain  is  only  the 
highest  degree  of  excitation  of  the  skin,  whether  by  pressure 
or  by  change  of  temperature ;  while  any  excitation,  of  what- 
ever nature,  will  excite  the  same  sensation  in  a  lower  degree ; 
thus,  if  a  part  of  the  skin  be  covered  with  a  card,  in  which  a 
very  small  hole  is  made,  and  an  excitant  of  any  kind  brought 
to  bear  upon  that  portion  of  the  skin  which  is  exposed 
through  this  hole,  there  will  be  no  difference  between  the 
sensations  produced,  whether  they  be  caused  by  the  applica- 
tion of  a  red-hot  coal,  the  prick  of  a  pin,  or  by  tickling  with 
a  feather,  etc.  In  spite  of  this  experiment,  however  (experi- 
ment by  Fick),^  we  can  hardly  admit  that  all  these  sensations 
are  of  the  same  kind,  and  differ  only  in  degree,  when  we  see 
that  in  certain  pathological  cases  they  may  be  independently 
paralyzed,  or  that  special  subjective  sensations  may  be  pro- 
duced.    It  is  especially  difficult  to  admit  that  pain  is  only 

1  See  H.  Taine,  "  De  1 'Intelligence."  Paris,  1870,  Vol.  II.  Book 
in.     Sensations  du  Toucher. 


SENSE   OF  TASTE.  401 

the  result  of  excitation  carried  to  the  highest  degree,  for 
many  instances  are  known  of  the  sensibility  to  pain  ceasing 
entirely  (analgesia),  while  all  other  forms  of  sensibility  (touch, 
tickling,  to  temperature)  remained :  in  this  case  we  must  con- 
clude that  tlie  nerve  terminations  have  lost  their  suscepti- 
bility to  the  higher  degrees  of  excitation,  while  they  are  still 
capable  of  being  affected  by  the  lower. 

II.   The  Sense  of  Taste. 

The  sense  of  taste  is  the  result  of  special  impressions  pro- 
duced by  certain  sapid  substances ;  it  is,  however,  difficult 
exactly  to  define  a  sapid  substance,  and  to  analyze  the  interior 
phenomenon  of  the  impression  produced  by  it;  there  is,  also, 
some  difference  of  opinion  in  regard  to  the  subject  of  dis- 
tinguishing between  the  true  sapid  substances,  and  those 
whicli  only  excite  the  general  or  tactile  sensibility  of  the 
orgnn  of  taste. 

The  exclusive  seat  of  taste  is  in  the  mouth.  The  palate  is 
commonly  spoken  of  as  the  seat  of  this  function,  but  physiolog- 
ical experiments  have  proved  that  the  sense  of  taste,  jK>ar  excel- 
letice^  resides  only  in  the  tongue^  and  is  even  restricted  to 
certain  parts  of  this  organ.  In  general,  when  we  wish  to 
taste  any  substance,  w^e  place  it  upon  the  tongue  and  apply 
the  latter  to  the  palate,  in  order  to  compress  the  sapid  sub- 
stance, and  thus  increase  its  points  of  contact  with  the  gus- 
tatory surface ;  it  is  on  account  of  this  that  the  palate  has 
been  wrongly  supposed  to  have  an  office  to  perform  in  tast- 
ing in  addition  to  this  simple  mechanical  duty. 

A  fruitful  cause  of  mistake,  and  one  which  ought  to  make 
us  distrust  many  experiments,  lies  in  the  fact  that  sensations 
have  been  often  mistaken  for  taste^  while  these  were  only 
produced  by  the  general  or  tactile  se7isibiUty  of  the  tongue. 
We  have  seen  that  this  organ,  especially  its  tip,  must  be 
classed  as  the  most  important  among  the  organs  of  touch : 
certain  sensations,  dignified  with  the  name  of  tastes,  are 
caused  by  this  sensibility,  such  as  the  farinaceous  savor  re- 
sulting from  the  mechanical  impression  produced  by  a  sub- 
stance divided  in  small  pieces,  and  the  gummy  taste  of 
substances  in  a  more  or  less  sticky  condition.  What  is 
known  as  Vi  fresh  or  cooling  taste^  is  only  the-  thermal  effect 
])roduced  by  the  absorption  of  caloric,  caused  by  a  substance 
in  dissolving  (such  as  the  taste  of  nitre),  or  in  evaporating 
(as  the  taste  of  the  essential  oils).     We  speak  also  of  acrid 

26 


402  ORGANS  OF  THE  SENSES. 

tastes  ;  but  these  are  a  feature  of  general  sensibility :  a  sub- 
stance of  an  acrid  taste  has  a  tendency  to  destroy  the  raucous 
surface,  as  if  by  a  blister;  we  therefore  designate  as  acrid 
those  substances  which  modify,  eat  into,  or  dissolve  the  epi- 
thelium. 

On  the  other  hand,  sensations  arising  only  from  some  im- 
pression made  upon  the  organ  of  smell  are  frequently  mistaken 
for  gustatory  impressions ;  the  organs  of  taste  and  smell  are 
situated  so  near  each  other,  that  it  would  seem  that  their 
sensations  must  be  connected.  Aromatic,  nauseous  sensa- 
tions, etc.,  belong  to  this  class:  thus  roast  meats,  cheese, 
some  vinous  and  other  drinks,  owe  their  sapid  properties  to 
the  development  of  fatty  acids  or  peculiar  odoriferous  ethers. 
If  we  stop  up  the  nostrils  while  eating,  or  have  simply  a  cold 
in  the  head,  we  find  that  most  alimentary  substances  lose 
their  taste. 

It  is  more  difficult  to  decide  whether  salt,  alkaline,  and 
acid  savors  are  actually  gustatory  sensations,  or  sensations  of 
touch  in  a  disguised  form.  Schiff  considers  them  to  be  really 
gustatory  impressions,  because  they  are  not  perceived  as  such 
when  the  cutaneous  surface  is  excoriated,  and  also  because 
they  are  produced  by  the  exciting  influence  of  the  galvanic 
current :  we  know  that  this  current  gives  rise  to  gustatory 
sensations  which  are  not  caused  by  the  electrolytic  decom- 
position of  the  buccal  liquids,  and  which  consist  essentially 
in  an  acid  taste  at  the  positive  pole,  and  an  alkaline  taste  at 
the  negative  pole.  However  this  may  be,  the  acid  and  alka- 
line sensations  form  a  transition  to  the  really  gustatory  sen- 
sations. 

By  excluding  all  the  so-called  savors  which  are  produced 
by  such  impressions  as  we  have  mentioned,  we  arrive  at  the 
conclusion  that  there  are  really  only  two  distinct  tastes, 
sweet  and  hitter,  and  only  two  kinds  of  really  sapid  bodies, 
sweet  and  hitter.  There  is  nothing  to  be  said  in  general  as 
to  those  substances,  between  which  there  appears  to  be  no 
chemical  connection  ;  for  we  find  bodies  in  the  class  of  chem- 
ical substances  which,  in  a  chemical  point  of  view,  are  most 
dissimilar,  such  as  salts  of  lead,  sugars,  properly  so  called,  and 
a  number  of  alcohols  (glycerine). 

By  experimenting  with  these  substances  we  find  that  the 
posterior  part  of  the  upper  surface  of  the  tongue,  its  lower 
surface,  and  the  frenum  have  no  power  to  cause  sensation  of 
taste ;  this  latter  is  confined  to  the  edges  of  the  tongue,  espe- 
cially to  the  ti}).     In  these  parts,  beside  the  filiform  or  con- 


SENSE  OF  TASTE. 


408 


^ry 


Fig.  103.  — Lingual  papillse. 
andBowmau.)* 


(Todd 


ical  papillce  which  are  everywhere  met  with,  and  of  which 
we  spoke  in  relation  to  the  sense  of  touch,  we  find  two  some- 
what peculiar  forms  of  papillae,  the  fungiform^  and  the 
circumvallate    (Fig.  103).  ^ 

The     fungiform     papillae  * 

somewhat  resemble  a 
mushroom,  having  a  short 
pedicle,  and  a  globular 
head,  in  which  the  dermis 
forms  a  number  of  second- 
ary papillae,  resting  in  a 
bed  of  epithelium,  with 
which  the  organ  is  uni- 
formly covered  (Fig.  103, 
B.).  The  circumvallate 
papillae  resemble  these, 
though  they  are  wider  and 
flatter,  and  are  imbedded 
in  an  excavation  in  the 
raucous  tissue  (calices),  be- 
yond which  they  scarcely 
project  at  all;  they  also  exhibit  a  number  of  secondary 
papillae,  covered  by  the  epithelium  (Fig.  103,  C).  A  number 
of  nerve  filaments  terminate  in  these  papillae,  but  whether  by 
true  extremities,  by  corpuscles  similar  to  those  of  touch,  or 
by  union  of  the  epithelial  cells,  remains  still  undecided.^ 

These  papillae  are  placed  upon  the  back  of  the  tongue,  the 
fungiform  being  arranged  in  the  form  of  a  quincunx  along 
the  sides  of  this  organ ;  their  number  varies  in  different  per- 
sons, the  circumvallate  or  large  papillae  are  arranged  in  two 
rows,  which  meet  at  the  base  of  the  tongue  (foramen  caecum), 
in  a  form  like  that  made  by  the  union  of  the  two  arms  in  the 
letter  V  (Fig.  104). 

We  have  already  remarked  that  the  sense  of  taste  resides 
only  in  those  parts  in  which  these  papillae,  especially  the  cir- 
cumvallate^  are  found,  that  is,  at  the  base  of  the  tongue ;  for 
this  reason,  tastes  are  most  clearly  perceived,  and  in  the  most 
agreeable  manner,  at  the  commencement  of  deglutition,  when 
the  alimentary  substances  come  in  contact  with  the  V-shaped 
row.  This  row  of  large  papillce  appears  to  be  the  special 
seat  of  the  impression  produced,  especially  when  made  by 

»  See  Art.  Gout,  in  Vol.  XVI.  of  the  '*  Nouveau  Diet,  de  Mdd. 
et  de  Chirur.  Pratiques. "     1872. 

*  A,  Filiform  papji'  i.    B,  Fungiform  papilla.    C,  Circumvallate  papilla. 


404  ORGANS  OF  THE  SENSES. 

bitter  substances,  for  when  their  innervation  has  been  de- 
stroyed, the  animal  will  swallow  bitter  substances  without  any 
apparent  repugnance.    The  sensatioiis  of  nausea,  whicli  give 


Pig.  104.  —  Tongue,  with  its  papillae  and  nerves.   (L.  Hirschfeld  and  Leveille).* 

rise  to  the  antiperistaltic  movement  of  deglutition,  of  vomit- 
ing, also  take  place  chiefly  in  this  part ;  but  these  are  phe- 
nomena of  ordinary  sensibility,  for  if  the  finger  be  placed  at 
the  back  of  the  mouth,  this  reflex  action  will  be  produced,  and 
Ftill  better  if  the  uvula  be  touched  instead  of  the  base  of  the 
tongue. 

Snpid  bodies  must  be  dissolved  in  order  to  be  tasted :  the 
secretion  of  the  saliva  is,  tlierefore,  necessary  to  gustation, 
and  if  tlie  moutli  be  dry,  the  substance  received  will  make 
little  impression.  The  impressions  made  by  sapid  substances 
are,  therefore,  peculiarly  fitted  to  produce  the  reflex  phenom- 
enon of  the  salivary  secretion,  especially  the  sub-maxillary 
secretion,  as  we  know  that  the  sight  or  remembrance  of  a 
favorite  dish  will  sometimes  make  the  mouth  water ;  thus, 
if  a  piece  of  meat  be  shown  to  a  dog,  the  saliva  is  seen  to 
flow  freely  from  a  tube  inserted  in  the  duct  of  the  sub-maxil- 

*  1,  Hypoglossal  nerve.  2,  Lingual  branch  of  the  tri-geminus.  3.  Lingual 
branch  of*  the  glosso-pharyngeal  nerve.  4,  Chorda  tympani.  8,  Sub-maxil- 
lary ganglion.  11,  Anastonioses  of  the  lingual  with  the  hj'poglossal  nerve.  12, 
Facial  nerve.  13,  Mucous  membrane  detached  and  thrown  upwards :  the  circum- 
vallate  papilla;  are  seen  behind. 


SENSE  OF  TASTE.  405 

lary  gland,  for  which  reason  CI.  Bernard  has  suggested  that 
this  gland  should  be  considered  as  essentially  connected  with 
the,  functions  of  gustation. 

The  nerves  of  taste  are  the  Ungual  and  the  glosso-pharyn- 
geal  nerves.  The  lingual,  which  is  a  branch  of  the  trigeminus, 
extends  to  the  posterior  part  of  the  tongue,  imparting  to  it 
general  and  tactile  sensibility,  as  well  as  taste.  The  glosso- 
pharyngeal nerve  extends  to  the  base,  and  regulates  the 
gustatory  sensibility  of  the  large  papillae  (Fig.  104).  It 
is  this  nerve,  chiefly,  which  transmits  the  impressions  made 
by  bitter  substances :  for  this  reason  it  has  been  called,  too 
exclusively,  as  it  would  seem,  the  nauseant  nerve.  The  lin- 
gual and  glosso-pharyngeal  nerves  thus  govern  equally  the 
sense  of  taste,  and  both  possess  fibres  of  general  sensibility , 
but  that  the  fibres  of  feeling  or  general  sensibility  are  quite  dis- 
tinct from  the  fibres  of  taste  is  apparently  proved  by  the  fact 
that  one  of  these  senses  {taste)  may  entirely  cease,  while  the 
general  sensibility  and  power  of  sensation  in  the  tongue  con- 
tinue unimpau'ed. 

The  question  has  arisen  whether  it  would  not  be  possible  to 
separate  the  fibres  of  taste  from  the  fibres  of  touch  in  the  glosso- 
pharyngeal and  the  lingual  nerves.  No  method  is  as  yet  known  by 
which  the  former  may  be  separated,  but  the  study  of  paralysis  of 
the  facial  nerve  in  the  posterior  part  of  the  tongue,  the  region 
innervated  by  the  lingual  nerve,  this  paralysis  being  accompanied 
by  the  loss  of  taste,  has  led  to  the  belief  that  the  solution  may 
possibly  be  found  by  studying  the  chorda  tympanic  a  small  nerve 
thread  which,  beginning  in  the  facial  nerve,  traverses  the  middle 
ear,  and  joins  the  lingual  nerve  at  the  level  of  the  pterygoid 
muscles  (Figs.  105  and  lOG). 

The  study  of  the  functions  of  the  chorda  tympani  is  one  of  Lhe 
most  delicate  questions.  We  have  already  spoken  of  the  office  of  this 
nerve  or  cord  in  reference  to  the  secretion  of  the  saliva.  We  w  ere 
then  seeking  to  discover  whether  all  the  fibres  of  this  nerve  cease 
at  the  level  of  the  submaxillary  gland,  or  whether  any  of  them  go 
beyond  this,  and  extend  to  the  tongue.  In  spite  of  numerous  con- 
tradictory experiments,  physiologists  now  nearly  all  agree  in  the 
opinion  that  the  chorda  tympani  does  extend  to  the  tonj^ue. 
Vulpian  and  Prevost  have  constantly  found  degenerated  nerve 
fibres  in  the  terminal  branches  of  the  lingual  nerve,  after  the 
chorda  tympani  had  been  destroyed,  either  by  being  cut  in  the  ear, 
or  by  the  removal  of  the  facial  nerve :  these  degenerated  fibres  can 
only  arise  from  the  chorda  tympani. 

The  next  inquiry  to  be  made  was  whether  the  chorda  tympani  is 
united  to  the  tongue  as  a  motor  or  as  a  sensory  nerve.  The  latter 
function  is  now  assigned  to  it  by  some  physiologists,  especially 
Lussana  and  Schiff,  both  of  whom  maintain  that  the  chorda  tympani 


406  ORGANS  OF  THE  SENSES. 

is  not  only  a  nerve  of  sensibility,  but  one  of  special  sensibility,  as 
it  is  the  principal  organ  of  taste.  Lussana  and  Inzani  mention 
("  Archives  de  Physiologic, "  18{J9  and  1872)  the  case  of  a  person 
in  whom  the  chorda  tympani  had  been  cut  in  an  operation  per- 
formed on  the  middle  ear  by  a  quack.  After  the  operation  the 
posterior  two-thirds  of  the  corresponding  half  of  the  tongue  were 
found  to  have  lost  the  sense  of  taste^  while  retaining  an  imim- 
paired  sensibility  to  touch  and  to  pain.  Lussana  has  since  collected 
several  similar  observations  in  cases  in  which  the  paralysis  of  the 
facial  nerve,  following  a  wound  or  an  operation,  was  accompanied 
by  the  partial  loss  of  the  sense  of  taste.  Lussana  made  the  experi- 
ment of  performing  the  bilateral  extirpation  of  the  glosso-pha- 
ryngeal  nerves  in  a  dog,  and  afterwards  cutting  the  two  chordae 
tympani.  The  result  of  this  experiment  showed  that  the  sense  of 
taste  entirely  disappeared  while  the  posterior  portion  of  the  tongue 
retained  its  sensibility  to  touch  and  pain.  In  a  counter-experiment 
Schiff  ("  Physiologic  de  la  Digestion,"  Florence,  1866,  Vol.  I.) 
succeeded  in  cutting  the  lingual  nerve  above  its  junction  with  the 
chorda  tympani,  close  to  the  base  of  the  skull;  the  tactile  and 
painful  sensibility  of  the  corresponding  portion  of  the  tongue 
ceased  entirely,  while  traces  of  the  sense  of  taste  remained;  these, 
though  sometimes  extremely  slight,  could  be  always  recognized  by 
the  movements  and  contortions  of  the  animal  subjected  to  the  in- 
fluence of  acid  or  bitter  substances. 

Lussana  and  Schiff  conclude  from  this,  that  the  lingual  nerve 
governs  only  the  general  sensibility  of  that  portion  of  the  tongue  through 
which  it  spreads^  and  has  no  gustatory  fibres  of  its  own^  these  fibres 
proceeding  from  the  chorda  tympani. 

This  conclusion,  unfortunately,  loses  something  of  its  value 
from  the  circumstance  that  it  necessitates  a  condition  which  it  is 
almost  impossible  to  satisfy  in  the  present  state  of  science.  What 
course  do  the  gustatory  fibres  of  the  chorda  of  the  tympani  follow 
in  proceeding  to  the  nerve  centres?  Are  they  represented  by  the 
intermediate  nerve  of  Wrisberg?  or  do  the^  arise  from  an  intra- 
cranial anastomosis  of  the  facial  nerve  with  a  sensory  nerve,  a 
branch  of  the  trifacial  ? 

Lussana  has  no  hesitation  in  adopting  the  former  hypothesis, 
and  he  has  helped  to  strengthen  it  by  a  number  of  experiments,  in 
some  of  which  the  trifacial  was  entirely  destroyed,  the  taste  re- 
maining uninjured,  while,  in  others,  intra-cranial  lesions  (lesions 
of  central  portion)  of  the  facial  nerve  are  accompanied  by  a 
change  in  the  sense  of  taste. 

The  number  of  experiments,  however,  which  have  produced  an 
entirely  opposite  result  are  much  more  numerous  than  these.  The 
cases  reported  by  Davaine,  Gueneau  de  Mussy,  and  Roux,  the 
experiments  made  by  Biffi  and  Morganti,  and  Schiff 's  researches,^ 
all  seem  to  prove  that  lesion  of  the  central  portion  of  the  facial 
nerve  produces  no  effect  upon  the  sense  of  taste;  and  that,  conse- 

i  See  Art.  "Goiit,"  in  the  ''Nouveau  Dictionnaire  do  Mdd.  et  de  Chirur. 
Pratiques,"  Vol.  XVI. 


SENSE  OF  TASTE. 


407 


quently,  the  chorda  tympani,  according  to  Schiff,  consists  of  bor- 
rowed fibres  proceeding  from  the  trifacial  to  the  facial  nerve,  a 
lesion  or  entire  section  of  the  trifacial,  before  its  division  into  three 
branches,  producing  the  same  effect  on  the  taste  as  section  of  the 
chorda  tympani. 

By  accepting  this  conclusion,  however,  we  only  place  the  diffi- 
culty a  little  farther  back ;  for  the  new  question  immediately  arises, 
where  and  how  does  the  facial  nerve  borrow  from  the  trifacial  the 
sensory  fibres  which  are  destined  to  form  the  chorda  tympani? 

Schiff  inclines  to  the  belief  that  in  the  large  petrosal  nerve  an 
anastomosis  takes  place,  by  means  of  which  the  facial  nerve  bor- 
rows from  the  trifacial  the  sensory  fibres  which  lead  to  the  tongue. 
So  much  controversy  is  still  going  on  in  regard  to  these  results 
that  we  refrain  from  giving  the  details  of  the  experiments  under- 
taken for  the  purpose  of  proving  these  theories.  We  will  simply 
sum  up  in  a  diagram  the  theories  of  Lussana  and  of  Schiff'.     In 


•VTL 


the  figures  105  and  106,  G  represents  the  Gasserian  ganglion, 
developed  on  the  trifacial  (HI) ,  which  then  divides  into  the  ophthal- 
mic (1),  the  superior  maxillary  (2),  and  the  inferior  maxillary  (3) ; 
L  represents  the  lingual  nerve;  VII,  the  facial;  i,  the  intermediate 
nerve  of  Wrisberg;  GT,  the  chorda  tympani;  Gg,  the  genicu- 
late ganglion.  We  see  that,  in  Lussana's  hypothesis  (Fig.  105), 
the  gustatory  fibres,  the  course  of  which  is  represented  by  a  dotted 
line,  pass  from  the  tongue  to  the  nerve  centres  through  the  lin- 
gual nerve  (L),  the  chorda  tympani  (CT),  the  facial  nerve,  and, 
finally,  through  the  intermediate  nerve  of  Wrisberg.  On  the 
other  hand,  Schiff  maintains  that  the  paths  of  conduction  of  the 
sensory  impressions  follow  the  lingual  (L,  Fig.  107),  the  chorda 
tympani  (CT),  and  the  facial  nerve  (VII);  but  they  leave  this 
nerve  at  the  level  of  the  geniculate  ganglion  (Gg),  and  follow  the 
large  petrosal  nerve,  join  the  ganglion  of  Meckel  (M),  and,  conse- 
quently, the  superior  maxillary  (2),  and,  finally,  reaches  the  base 
of  the  cncephalon  by  the  trunk  of  the  trifacial  (III). 

We  must,  however,  add  that  physiologists  by  no  means  gener- 


408 


ORGANS  OF  THE  SENSES. 


ally  acknowledge  the  sensory  functions  of  the  chorda  tympani. 
The  most  recent  experiments  on  this  subject  are  those  made  by 
Vulpian,  who  considers  the  filaments  leading  from  this  nerve  to  the 
tongue  as  similar  to  those  which  pass  from  it  to  the  sub-maxiliary 
gland  (Soc.  de  Biologic,  187;>).  By  exciting  these  filaments  in  the 
corresponding  half  of  the  organ,  Vulpian  produced  phenomena 
similar  to  those  which  take  place  in  the  sub-maxillary  gland  dur- 
ing the  galvanization  of  the  same  nerve;  in  other  words,  the  tongue 
grows  red  and  heated  on  the  side  galvanized.  The  chorda  tympani 
is,  therefore,  a  vaso-motor  nerve,  which  here  also  regulates  the 
dilatation  of  the  vessels  (see  p.  IT")).  We  see  in  this  way  how 
facial  paralysis  may  affect  the  sense  of  taste,  the  function  of  the 
lingual  mucous  being  undoubtedly  influenced  by  the  vascularization 
of  this  tissue. 

III.    Sexse  of  Smell. 

The  sense  of  smell  is  one  which  gives  rise  to  certain  per- 
ceptions known  as  odors ;  it  is,  however,  still  more  difficult 


Fig.  107.  — External  wall  of  the  nasal  chambers  with  the  three  spongy 
or  turbinated  bones  and  the  three  meatus.* 

to  define  exactly  nn  odorous  substance,  and  the  nature  of  the 
impressions  produced  by  it,  than  to  define  a  sapid  substance 

*  fT,  Olfactory  nerve,  b,  Olfactory  bulb  upon  the  cribifonn  plate  of  the 
ethmoid:  below  is  seen  the  plexiform  (lisposition  of  the  olfactory  branches  upon 
the  upper  and  the  tniddlu  turbinated  bones,  o.  Nerve  of  the'  fifth  pair,  with 
Gasserian  ganj^lion.  «<,  Its  palatine  branches  { upper  maxillary  and  their  pitui- 
tary lilaments. 


SENSE  OF  SMELL. 


409 


and  its  effects.  Smells  cannot  be  divided  into  classes,  and, 
setting  aside  the  arbitrary  and  special  appellation  of  agree- 
able and  disagreeable  odors,  we  can  distinguish  them  only  by 
the  names  of  the  bodies  to  which  they  belong. 

The  sense  of  smell  resides  in  the  nasal  chambers  (Fig.  107), 
but  only  a  small  part  of  this  cavity  serves  for  the  purpose, 
the  remainder  either  giving  rise  to  the  resonance  of  the  voice 
(especially  the  annexed  cavities:  maxillary,  frontal  sinus, etc.), 
or  preparing  the  air  inhaled  by  imparting  to  it  the  degi-ee 
of  heat  and  moisture  necessary  to  the  respiratory  mucous 
membrane,  as  we  learned  when  studying  that  mucous  tissue 
(p.  286).  These  parts  are  formed  by  three  turbinated  bones, 
one  above  the  other,  which  enclose  rather  narrow  ^assa^es 
(Fig.  109),  the  whole  being  lined 
with  an  extremely  soft,  thick,  vas- 
cular mucous,  containing  lich  ve- 
nous plexus,  and  coated  with  a  co- 
lumnar epitheliitm  having  vibratile 
cilia ;  these  latter  are  also  found 
in  the  remainder  of  the  conducting 
tube  of  the  respiratory  tree,  of 
which  this  part  of  the  nasal  cham- 
bers forms  the  beginning.  In  this 
mucous  (Schneiderian  membrane) 
are  found  numerous  glands,  which 
help  to  keep  moist  the  sui-fhce 
Avhich  would  otherwise  be  dried  by 
the  movement  of  the  air. 

The  sense  of  smell  itself  appears 
to  be  intended  as  a  guard  to  the  purity  of  the  air  inhaled : 
for  most  substances  which  are  capable  of  vitiating  the  air, 
have  some  odor,  and  are  naturally  under  the  control  of  the 
sense  of  smell. 

The  sense  of  smell  resides  only  in  the  highest  portion  of 
the  nasal  chambers,  in  those  parts  through  which  the  olfac- 
tory nerve,  the  nerve  of  special  sensibility,  extends,  while  the 
lower  parts  receive  only  the  branches  of  the  trifacial  nerve 
or  tlie  nerves  of  general  sensibility  (see  Cranial  Nerves,  pp. 
35-38).    In  this  region   (called  the  olfactory  region,  of  a 


Fig.  108.  —  Diagram  of  transverse 
section  of  the  nasal  chambers.* 


*  1,  Inferior  turbinated  bone.  2,  Middle  turbinated  bone.  3,  Superior  tur- 
binated bone. 

A,  Thickness  of  the  mucous  membrane  and  soft  parts  (which  are  very  vas- 
cular) with  which  it  is  lined.  B,  Skeleton  (bones  or  cartilages).  C,  Partition, 
showing  the  same  parts  (mucous  membrane  and  skeleton). 


410  ORGANS  OF  THE  SENSES. 

yellow  color  in  animals),  the  raucous  surface  changes  its  na- 
ture :  here  (the  upper  part  of  the  septura  within,  and  the 
two  superior  turbinated  without),  this  membrane  is  much 
less  vascular,  containing  fewer  glands  and  no  vibratile  cilia, 
but  having  simply  a  columnar  epithelium  ;  its  characteristic 
feature  consists  in  the  terminal  branches  of  the  olfactory 
nerves,  these  fibres  being  so  fine  and  so  numerous  that  by 
their  presence  alone  an  experienced  histologist  will  recognize 
a  detached  fragment  of  this  olfactory  membrane.  These 
nerve  fibres  appear  to  terminate  at  the  surface  by  joining  the 
deep  and  slender  extremity  of  the  columnar  epithelial  cells ; 
at  all  events,  Schultze's  researches  seem  to  show  that  around 
the  epithelial  cells  of  this  region  are  found  special  organs 
{olfactory  cells  of  Schultze)  or  fusiform  elements,  elongated, 
having  a  rounded  protuberance  in  the  middle  with  a  nucleus, 
the  two  extremities  being  prolonged  in  fibrillae.  The  exter- 
nal prolongation,  which  is  the  thicker  of  the  two,  passes  be- 
tween the  epithelial  cells  to  the  free  surface,  while  the 
internal  prolongation  appears  to  continue  with  the  fibres  of 
the  olfactory  nerve.  This  appears  to  be  a  well-established 
instance  of  the  relation  between  the  nerves  and  the  epithe- 
lium, and  it  serves  to  explain  the  importance  of  the  latter  to 
all  the  organs  of  the  senses. 

The  sense  of  smell  is  exercised  either  upon  vaporous  sub- 
stances floating  in  the  air,  or  imperceptible  solid  molecules 
which  the  air  carries  along  with  it ;  volatile  bodies  are,  there- 
fore, generally  odorous.  It  has  been  observed  that  the  sense 
of  smell  is  aided  by  moisture,  and  also  that  flowers  are  more 
fragrant  in  damp  weather  than  in  dry.  On  the  other  hand, 
if  the  quantity  of  vapor  is  too  great,  or  if  water  is  intro- 
duced into  the  nasal  chambers,  the  sense  of  smell  is  hindered, 
or  even  ceases  entirely,  until  the  normal  condition  is  restored 
(the  sense  of  smell  is  not  so  acute  in  foggy  weather). 

The  conditions  under  which  vapors  or  odorous  particles 
must  be  brought  in  contact  with  the  olfactory  surface  in 
order  to  produce  the  necessary  sensation  are  somewhat 
peculiar  and  extremely  restricted:  they  must  be  brought 
by  a  current  of  air,  and  they  can  act  only  while  this  current 
is  in  motion ;  thus,  if  a  piece  of  camphor  is  placed  in  the 
nose  while  the  air  is  quite  still,  no  sensation  is  j^roduced,  and 
the  case  is  the  same  if  the  nasal  chambers  are  filled  with  an 
extremely  fragrant  volatile  fluid.  In  order  to  smell  perfectly, 
therefore,  we  inhale  the  air  by  means  of  short  successive  in- 
spirations.    This  is  because,  in  the  second  place,  the  current, 


iSENSE   OF  SMELL.  411 

of  air  must  be  sloio  and  feeble.  Still  more  peculiar,  however, 
is  it  that  this  current  of  air  must  be  inhaled,  and  must  pro- 
ceed from  in  front  to  back,  no  doubt  because  it  is  then  bro- 
ken against  the  spur  which  forms  the  anterior  part  of  the 
inferior  turbinated  bone,  and  thus  portions  of  it  rise  easily 
to  the  olfactory  membrane.  The  air  exhaled  through  the 
posterior  cavity  of  the  nasal  chambers  produces  no  impression 
in  passing  through,  whatever  may  be  the  quantity  of  odorous 
particles  that  it  may  contain ;  the  same  is  true  if,  by  any 
artificial  means  (injection  or  insufflation),  a  current  of  air  is 
directed  upon  the  olfactory  mucous,  either  through  the  open- 
ing of  the  nostrils,  or  through  a  passage  made  in  the  frontal 
and  the  frontal  sinuses.  These  facts  are  well  known  to  epi- 
cures, who,  when  they  desire  to  try  the  flavor  of  a  wine,  do 
not  breathe  into  the  nasal  chambers  through  the  posterioj 
orifices,  but  breathe  gently  forwards  and  upwards  through 
the  orifice  of  the  mouth,  and  draw  in,  very  slowly  and  by 
short  jerks,  the  air  which  comes  in  contact  with  their  nos- 
trils. 

We  have  seen  that  the  seat  of  smell  corresponds  exactly 
with  the  distribution  of  the  olfactory  nerve.,  which  justifies 
us  in  considering  this  nerve  as  governing  this  special  sensa- 
tion. Magendie  supposed  the  sense  of  smell  to  reside  in  the 
trifacial ;  his  reason  for  this  was  that,  having  cut  the  nerve 
of  the  first  pair  (the  olfactory)  in  a  dog,  and  then  held  some 
ammonia  to  its  nose,  the  animal  drew  back  and  shook  its 
head ;  this,  however,  as  in  the  case  of  the  tongue,  was  a  phe- 
nomenon of  general,  not  of  special,  sensibility :  the  caustic 
vapors  of  the  ammonia  acted,  not  on  the  sense  of  smell,  but 
on  the  sensibility  of  the  Schneiderian  membrane  in  general, 
which  is  innervated  by  the  trifacial  nerve. 

Some  clinical  observations  have,  however,  thrown  some 
doubts  upon  the  functions  of  the  olfactory  nerve,  considered 
as  an  organ  of  smell :  the  most  curious  of  these  cases  is  that 
of  the  autopsy  of  a  woman,  in  whom  CI.  Bernard  found  the 
bulb  and  the  olfactory  trunk  entirely  wanting,  and  the  corre- 
sponding part  of  the  ethmoid  bone  imperforate ;  the  strict 
inquiry,  however,  established  the  fact  that  this  person's  sense 
of  smell  had  been  perfect  during  life,  and  that  no  peculiarity 
in  this  respect  had  ever  been  observed  in  regard  to  her. 
Instances  of  this  kind  cannot  be  explained,  but  some  ex- 
periments seem  to  confirm  the  opinion  that  the  olfactory 
nerve  has  an  office  of  special  sensibility.     Schiff  took  five 


412  ORGANS  OF  THE  SENSES. 

young  dogs,  in  four  of  which  he  made  an  intra-cranial  section 
of  the  first  pair,  while  he  cut  only  the  posterior  roots  of  the 
olfactory  branch  of  the  fifth ;  he  found  that  the  latter  retained 
its  sense  of  smell,  while  the  four  others  lost  it  entirely. 

The  sense  of  smell  is  much  more  acute  in  animals  than  in 
man ;  it  serves  them  as  a  valuable  guide,  and  is  the  moving 
cause  in  many  of  their  instinctive  and  deliberate  actions : 
thus  connected  with  the  sense  of  taste  it  enables  them  to 
distinguish  the  diflTerent  kinds  of  food  suited  to  them,  and  it 
is  the  agent  of  numerous  impressions  connected  with  the 
reproductive  functions,  etc.^ 

IV.   The  Sense  of  Hearing. 

Hearing  is  that  sense  by  means  of  which  we  are  conscious 
of  the  waves  of  sound  produced  by  the  vibration  of  bodies 
in  the  ambient  medium  (air  or  water). 

The  organ  of  hearing  is  extremely  complicated ;  in  order 
to  understand  it  we  will  first  examine  it  in  those  animals 
which  inhabit  the  water;  in  these  it  is  most  simple.  The 
essential  and  fundamental  part  of  the  organ  of  hearing,  as 
found  in  the  inferior  fishes,  consists  of  a  S7nall  hag  full  of 
fluids  in  which  nerve  fibres  terminate  in  connection  with  a 
special  epithelium,  furnished  with  prolongations  resembling 
great  cilia^  or  small  rocU^  that  vibrate  with  every  movement 
of  the  fluid.  The  waves  of  the  surrounding  medium  (fluid) 
are  thus  transmitted  almost  directly  to  the  nerve  termina- 
tions, and  excite  these  latter.  This  organ  is  found  in  all  the 
higher  animals  :  it  consists  of  the  saccule  or  smaller  vestibu- 
lar vesicle  and  the  utricule  or  common  sinus.  With  these 
are  connected  similar  dlcerticuli,  consisting  of  jiouches  of 
different  forms,  but  always  full  of  fiuid  {endolympli)  :  these, 
in  tlie  higlier  classes  of  fish,  are  the  membranous  semicircu- 
lar canals ;  in  reptiles,  and  especially  in  birds,  there  is  also 
a  peculiar  long  and '  exceedingly  complicated  canal  or  tube, 
which  is  wound  and  twisted  around  itself  like  a  spiral  stair- 
case, and  is  called  the  cochlea.  The  tube  of  this  cochlea  is 
also  divided  by  a  })artition  called  the  spiral  plate  (lamina 
spiralis  ossea)  into  two  secondary  tubes,  which  communicate 
with  each  other  at  the  summit  of  the  organ,  while,  at  the 
base,  one  connnunicates  with  the  rest  of  the  internal  ear  or 

^  See  G.  Colin,  "  Physiologie  comparce  des  Auimaux."  Vol. 
I.  p.  310. 


SENSE  OF  HEARING.  413 

vestibule  {scala  vestihuU)^  and  the  other  with  the  middle  ear 
or  tympanum  (by  the  fenestra  ovalis). 

This  collection  of  mem,dranotcs  pouches  (utricule  and  sac- 
cule), the  semicircular  canals  and  the  cochlea,  forms  the 
internal  ear  of  the  higher  vertebrate  animals.  The  auditory 
nerve,  or  nerve  of  the  eighth  pair,  terminates  here  in  organs 
differing  apparently  in  form,  but  belonging  all  to  the  same 
type,  viz.,  that  of  organs  capable  of  being  set  in  motion  by 
the  vibrations  of  the  fluid  in  which  they  are  immersed.  In 
the  membranous  pouches  (utricule  and  saccule)  these  organs 
consist  of  epithelial  cells  in  contact  with  crystals  of  carbonate 
of  lime  {otoliths),  which  strike  against  them  at  every  oscilla- 
tion of  the  fluid;  in  the  semicircular  canals  (in  the  am- 
pulloe),  they  consist  of  epithelial  cells  furnished  with  long 
rigid  cilia,  which  are  immediately  set  in  motion.  The  dis- 
position of  the  cochlea  is  more  complicated ;  the  cochlear 
branch  of  the  auditory  nerve  spreads  through  the  spiral 
membrane  (membrana  spiralis)  in  3000  or  4000  small  articu- 
lated organs  {organs  of  Corti),  which  cannot  here  be  de- 
scribed,^ but  which,  in  brief,  resemble  fragments  joined  to- 
gether like  the  beams  of  a  roof,  and  swing  to  and  fro  with 
the  oscillations  of  the  ambient  fluid.  The  whole  of  this 
internal  ear  or  labyrinth  arises  from  a  deep  vegetation  of 
the  integuments  of  the  lateral  portion  of  the  head  of  the 
embryo;  this  growth  is  afterwards  more  or  less  separated 
from  the  surface  from  which  it  sprang.  The  organ  of  Corti 
itself  is,  therefore,  an  epidermic  production. 

The  animals  which  live  -in  the  air  possess,  besides  the 
internal  ear,  an  additional  organ,  consisting  of  the  middle 
chamber  of  the  ear  or  drum  {tympa.num).  This  part,  which 
would  be  useless  in  water  animals,  for  whom  the  waves  of 
sound  are  communicated  readily  from  the  ambient  fluid  to 
the  fluid  ot  the  labyrinth,  is  necessary  to  facilitate  the  com- 
munication of  the  waves  of  a  gaseous  medium  to  the  fluid 
medium  of  the  organ ;  thus  we  know  that  sounds  do  not 
pass  readily  from  the  air  into  water.  The  middle  chamber  of 
the  ear  resembles  a  drum  hollowed  out  in  the  petrosal  substance 
and  contains  an  organ  of  conduction  intended  to  facilitate 
the  transmission  of  waves  of  sound  (Fig.  110)  ;  it  consists  of 
a  more  or  less  regular  bony  chain,  leading  from  the  internal 
ear  {fenestra  ovalis)  to  the  membrana  tympaiii  ;  this  latter 

^  See  Loewenberg,  "  La  Lame  spirale  du  Limagon."     ("  Joum. 
de  I'Anat.  et  de  la  Physiol."     186d.) 


414 


ORGANS  OF  THE  SENSES. 


membrane  comes  in  direct  contact  with  the  external  air, 
although  it  is  placed  at  one  end  of  a  collecting  and  concen- 
trating apparatus  (composed  of  the  pinna  or  am-icle  of  the 
ear  and  of  the  external  auditory  canal).  We  can  best  under- 
stand this  by  reducing  the  internal  ear  to  a  drop  of  liquid, 
and  supposing  a  vibrating  membrane  (membrane  of  the 
fenestra  ovalis  and  the  base  of  the  stapes)  which  vibrates  by 
the  intermediation  of  a  solid  chain,  the  chain  of  the  ossicles, 
the  other  extremity  of  which  is  connected  with  a  collecting 
organ,  the  memhrana  tympani,  and  the  cavity  of  the  concha. 
As  the  second  membrane  (the  deepest,  the  fenestra  ovalis)  is 


Fig.  109.  —Diagram  of  the  auditory  apparatus  in  man.* 

much  smaller  than  the  first  (membrane  of  the  tympanum  or 
drum),  the  slightest  vibration  of  the  latter  will  set  in  action 
the  former.  We  will  now  proceed  to  study  the  office  of  these 
parts,  taking  them  in  an  opposite  direction  or  from  without 
inwards,  which  is  the  direction  which  the  waves  of  sound 
follow. 

A.  External  ear. 

The  pinna  of  the  ear  or  concha  is  an  organ  which  has  little 
sensibility  of  its  own,  and  whose  general  and  tactile  sensibility 
is  somewhat  dull;  the  ornaments  with  which,  even  among  civil- 

*  From  right  to  left  are  seen  the  external  ear,  the  auditory  passage,  the  tym- 
panum with  the  chain  of  small  bones,  the  Eustachian  tube,  and  the  labyrintli. 
(Dalton,  "Human  Physiology.") 


SENSE  OF  HEARING.  415 

ized  n.'itions,  it  is  often  weighed  down,  scarcely  excite  any  sen- 
sibility in  it.  It  is  essentially  composed  of  a  cartilage,  folded  in 
a  peculiar  manner,  which  appears  to  constitute  it  an  organ  for 
collection  ;  both  its  direction  and  its  form  are  changed  in  ani- 
mals by  the  action  of  intrinsic  and  extrinsic  muscles,  which 
are  brought  into  play  according  to  the  degree  of  attention 
with  which  the  animal  listens  to  different  sounds.  In  man, 
these  muscles  are  rudimentary,  or,  at  the  most,  only  the  ex- 
trinsic muscles  contract  with  the  fronto-occipital  system,  when 
the  attention  to  any  sound  is  carried  to  its  highest  degree. 

This  pinna  is  thus  of  little  service  for  intensifying  sounds, 
and  those  who  are  deprived  of  it  do  not  experience  any 
sensible  change  in  their  power  of  hearing.  It  appears,  how- 
ever, to  be  of  use  in  enabling  us  to  judge  of  the  direction  of 
sounds:  a  person  deprived  of  it,  or  who,  for  the  sake  of 
experiment,  renders  it  useless  by  flattening  it  forcibly  against 
the  head,  or  by  filling  its  convolutions  with  wax,  will  find 
himself  unable  to  distinguish  the  direction  from  which  sounds 
proceed ;  there  is  no  doubt  that  we  judge  of  the  direction 
and  origin  of  sounds  by  the  slight  modifications  in  their  in- 
tensity produced  by  the  manner  in  which  the  sound-waves 
strike  the  pinna,  and  are  reflected  from  it.  We  judge  of 
their  direction^  also,  by  the  fact  that  the  sound  does  not 
strike  both  ears  alike :  it  rarely  happens  that  we  can  distin- 
guish whether  a  sound  proceeds  from  directly  before  us,  or 
directly  behind  us ;  we  therefore  turn  the  head  slightly,  and 
incline  the  ear  in  the  direction  from  which  we  suppose  the 
sound  to  come. 

The  external  auditory  canal  {meatus  auditorius  extemus) 
is  of  greater  importance ;  if  this  is  obstructed,  the  sense  of 
hearing  is  diminished,  and,  if  it  is  too  much  contracted,  deaf- 
ness sometimes  follows.^  It  furnishes  two  methods  by  which 
sounds  may  be  transmitted:  these  consist  of  the  column  of 
air  inside  it,  and  the  cartilaginous  and  bony  loalls  of  which 
it  is  formed ;  these  walls  transmit  the  waves  by  vibration, 
directly  to  the  bones  of  the  head,  and  thence  to  the  fluid  of 
the  labyrinth,  and  we  can  see  how  much  easier  the  transmis- 
sion must  take  place,  since  the  vibrations  spread  through 
solid  mediums.  This  auditory  canal  is  also  remarkable  ibr 
its  peculiar  sensibility :  at  its  opening  are  found  large  hairs, 
and  if  these  are  touched,  or  any  excitation  brought  to  bear 

1  See  P.  Bonnafont,  '*  Traits  des  Maladies  de  P Oreille."  1873, 
p.  120. 


416  ORGANS  OF  THE  SENSES. 

a  little  below  them,  strange  and  unexpected  reflex  phenomena 
will  follow,  such  as  a  feeling  of  nausea,  or  of  uneasiness  and 
general  discomfort,  which  warns  us  of  the  danger  to  which 
the  organ  of  hearing  is  exposed ;  these  are,  in  short,  phe- 
nomena of  general  sensibility,  and  have  no  connection  with 
the  sense  of  touch.  In  this  canal  (in  its  cartilaginous  and 
fibrous  portion)  are  found  the  cemminous  glands ;  we  ex- 
amined the  secretion  of  these  glands,  when  studying  the 
functions  of  the  skin,  and  found  it  the  thickest  and  most 
sticky  of  the  secretions  of  perspiration:  this  cerumen  serves 
to  prevent  any  substance  from  reaching  the  bottom  of  the 
external  auditory  canal,  where  its  presence  would  be  injuri- 
ous to  the  membrana  tympani. 

B.  Middle  chamber  of  the  ear. 

The  membrana  tympani  is  formed  of  connective  and  elastic 
fibres,  and  contains  a  large  number  of  vessels ;  here,  as  in  the 
case  of  the  pinna  of  the  ear,  the  abundance  of  the  vessels 
appears  to  be  intended  for  the  purpose  of  keeping  up  the 
temperature  of  these  parts  which  are  always  uncovered  and 
exposed  to  that  air  from  which  they  receive  vibrations.  The 
membrana  tympani  is  essentially  a  collecting  organ ;  it  is 
situated  at  the  bottom  of  the  external  auditory  canal,  but 
does  not  share  in  the  peculiar  sensibility  of  the  latter ;  if  an 
insect  penetrates  so  far  as  to  touch  it,  no  reflex  phenomenon  is 
produced,  but  only  a  sensation  resembling  that  accompanying 
a  sound,  and  which  is  caused  by  the  vibrations  communicated 
to  it.  It  is,  therefore,  simply  a  physical  organ,  for  the  recep- 
tion of  air,  or  of  the  sonorous  vibrations  from  the  walls  of  the 
canal. 

This  membrane  is  not  normally  so  situated  as  to  collect 
the  waves  of  sound,  but  appears,  on  the  contrary,  to  avoid 
them  up  to  a  certain  point,  being  oblique  from  top  to  bottom 
and  from  back  to  front ;  it  seems,  in  short,  to  continue  the 
supero-posterior  wall  of  the  canal ;  the  younger  the  subject 
the  more  decided  the  obliquity,  while  in  the /lei t^s  this  mem- 
brane is  nearly  horizontal.  It  is  not  a  plane,  but  consists  of 
a  very  low  cone^  having  its  internal  summit  slightly  flattened, 
and  its  edges  attached  to  the  deep  opening  of  the  external 
auditory  canal;  it  is  enclosed  in  a  sort  of  frame  which  appears 
distinctly  in  the  form  of  an  imperfect  ring  in  young  subjects. 
This  membrane  is,  therefore,  convex  on  the  interior^  its  con- 
vexity being  preserved  by  a  chain  of  small  bones,  a  portion 
of  which  (the  handle  of  the  malleus)  is  contained  in  the  thick 


SENSE  OF  HEARING. 


417 


part  of  the  membrane,  making  it  incline  inwards  (Fig.  110)  : 
this  convexity  or  tension  is  produced,  either  by  variations  in 
pressure  in  the  air  in  the  drum,  or  by  the  action  of  a  muscle 
(internal  muscle  of  the  malleus).  If  from  any  cause  the  air 
of  the  drum  becomes  rarefied,  the  exterior  air  presses  upon 
the  membrane,  forcing  it  deeper  into  the 
cavity  of  the  tympanum,  and,  conse- 
quently, stretching  it  while  increasing  its 
convexity  (in  the  direction  indicated  by  the 
arrows  in  Fig.  110).  The  internal  tnuscle 
of  the  malleus  (tensor  tympani)  produces 
the  same  effect :  it  draws  inwards  the  handle 
of  the  bone,  and  consequently  the  mem- 
brane, increasing  the  convexity  and  the  ten- 
sion of  the  latter.^  This  is  the  only  mus'cle 
whose  action  or  existence  has  been  satisfac- 
torily demonstrated ;  either  the  other  so- 
called  muscles  of  the  internal  chamber  of 
the  ear  have  no  existence  (anterior  and  ex- 
ternal muscles  of  the  malleus),  or  their 
action  is  not  yet  perfectly  understood 
(muscle  of  the  stapes,  stapedius).,  at  all 
events  they  do  not  produce  the  effect  of  re- 
laxing the  membrane,  which,  by  means  of  its  elasticity,  re- 
turns of  itself  to  the  position  of  repose  directly  its  tensor 
muscle  ceases  to  contract. 

The  purpose  of  this  temporary  tension  of  the  membrane  is 
now  easily  understood.  Bichat  supposed  that  the  tension  of 
the  membrane  must  be  increased  in  order  to  increase  the 
power  of  the  sound ;  this  hypothesis  is,  however,  contrary  to 
the  laws  of  physics,  and  Savart  has  shown  that  the  tension 


Fig.  110 
of  th< 
and  ossic 


Membrane 
of  the   tympanum 
'  les.* 


1  Some  persons  possess  the  power  of  contracting  the  musculus 
tensor  tympani  at  will,  and  thus  stretching  the  membrane  of  the 
tympanum.  This  tension  is  manifested  by  a  slight  cracking  sound, 
which  is  produced  in  the  ear  at  each  contraction  of  the  muscle:  the 
movements  made  by  the  membrane  under  the  influence  of  these 
voluntary  contractions  may  also  be  observed  by  the  aid  of  the 
speculum.  Nearly  all  those  physiologists  whose  attention  has 
been  directed  to  this  circumstance,  and  who  have  attempted  to 
produce  this  contraction,  have  succeeded  with  the  greatest  ease: 
Berard,  Miiller,  and  Wollaston  are  especially  mentioned  as  having 
done  so.     (Bonnafont,  op.  cit.,  p.  270.) 

b,  The  malleus,    c,  The  incus,    d,  Tlie 


*  aa,  Membrane  of  the  tympanum. 
stapes. 


27 


418  ORGANS  OF  THE  SENSES. 

of  the  membraDe  serves  to  diminish  the  effect  of  the  sound 
upon  it  (as  the  more  a  membrane  is  stretched,  the  less  fuU 
will  be  the  vibrations),  and  to  soften  certain  disngreeable 
sounds.  On  the  other  hand,  this  tension  makes  the  mem- 
brane vibrate  more  readily  to  acute  sounds;  and  to  hear 
these  demands  very  close  attention  (the  greater  the  tension 
of  a  membrane,  the  more  numerous  its  vibrations). 

Next  to  the  membrane  of  the  tympanum  comes  the  chain 
of  small  bones,  connecting  it  with  the  membrane  of  the  oval 
fenestra  (base  of  the  stapes).  In  the  inferior  animals,  this 
chain  simply  consists  of  a  straight  and  rigid  stalk  (as  found 
in  some  anourous  amphibians,  i\\Qpipa,  for  instance) ;  in  frogs 
it  takes  the  form  of  a  broken  line,  a  small  bone,  long  and 
curved,  and  which  is  called  the  columella  ;  in  man,  finally,  it 
is  formed  by  the  junction  of  three  small  bones  or  ossicles  (the 
malleus  or  hammer,  the  incus  or  anvil,  and  the  stapes)  :  these 
bones  are  articulated,  but,  in  regard  to  the  transmission  of 
sound,  they  may  be  considered  as  anchylosed,  it  having  been 
proved  that  these  articulations  do  not  directly  operate  for  the 
transmission  of  sounds. 

The  chain  of  ossicles  through  which  the  sound  waves 
chiefly  pass,  crosses  a  drum  filled  with  air,  called  the  tym- 
panic cavity;  it  is  flattened  from  without  inwards,  and,  like 
the  membrana  tympani,  exhibits  a  plane  oblique  to  the  exter- 
nal auditory  canal.  It  is  supposed  that  the  sound  waves  are 
not  only  transmitted  by  this  jointed  connecting-rod  of  bones, 
but  that  the  air  in  the  drum  also  serves  to  convey  them  to  the 
fenestra  rotunda  ;  this  is  possible,  but  not  very  probable,  and 
at  all  events,  this  mode  of  progression  must  be  only  secondary, 
for  the  round  fenestra  avoids  the  sound  waves,  as  it  were, 
being  hidden  beneath  the  promontory  (tuber  cochleie,  or 
projection  outwards  of  the  first  turn  of  the  cochlea  directly 
opposite  the  protuberance  of  the  membrana  tympani) ;  the 
correspondence  of  this  round  fenestra  with  one  of  the  open- 
ings of  the  cochlea,  which  communicates  on  the  other  side 
with  the  vestibule,  appears  to  be  intended  for  the  purpose  of 
giving  free  play  to  the  fluid  waves  which  pass  through  this 
complicated  organ.  Finally,  since  sound  is  more  readily 
transmitted  through  solids  than  through  fluids,  the  chain  of 
small  bones  must  have  a  much  more  important  office  to  fulfil 
than  the  air,  which  latter,,  no  doubt,  serves  only  as  an  insu- 
lating apparatus.  The  membrana  tympani,  and  these  ossi- 
cles, with  the  exception  of  the  stapes,  may  be  destroyed  with- 
out the  complete  abolition  of  hearing ;  it  will  only  be  more 


SENSE  OF  HEARING.  419 

or  less  obstructed.  The  loss  of  the  stapes  is  much  more 
serious,  and,  according  to  Bonnafont,  always  causes  deafness. 
This  fact  is  easily  explained;  the  stapes  is  attached  at  its 
base  to  the  oval  fenestra,  closing  it  entirely,  and  is  so  firmly 
fastened  to  it  that  it  cannot  be  removed  without  tearing  the 
membrane  of  the  oval  fenestra,  and  thus  allowing  the  endo- 
lymph  or  liquid  in  the  internal  ear  to  flow  out ;  it  is  not, 
therefore,  properly  speaking,  the  loss  of  the  bone  which 
occasions  deafness,  but  rather  the  escape  of  the  fluid  through 
the  aperture  made  by  the  ablation  (Bonnafont,  op,  cU.y  p. 
264). 

Two  organs  are  attached  to  the  middle  chamber  of  the 
ear :  these  are,  behind,  the  mastoid  cells,  which  are  irregular 
cavities,  or  sinuses  hollowed  out  in  the  mastoid  process  of 
the  temporal  bone ;  and,  in  front,  the  Eustachian  tube,  con- 
necting the  drum  of  the  tympanum  with  the  nasal  part  of 
the  pharynx. 

The  mastoid  cells,  being  full  of  air,  are  generally  considered 
as  a  resonant  organ  ;  this  supposition  has,  however,  no  other 
ground  than  the  fact  that  the  air  in  the  drum  vibrates,  and, 
consequently,  its  vibrations  are  intensified  by  those  of  the 
air  in  the  mastoid  cells.  "We  have  just  seen  that  the  vibra- 
tions of  the  air  in  the  drum  are  of  no  importance  whatever ; 
neither  have  diseases  of  the  mastoid  cells  furnished  any 
indication  as  to  the  purpose  of  these  cavities.  We  incline  to 
the  opinion  that  the  mastoid  cavities  are  empty  spaces,  hav- 
ing no  special  function,  and  intended  only  to  increase  the 
size  of  the  cavity  of  the  tympanum.  We  shall  presently  see 
that  in  the  normal  state  the  tympanum  is  closed  on  all 
sides ;  now,  as  the  tympanum  is  an  extremely  small  cavity, 
any  sudden  change  in  the  tension  of  this  thin  layer  of  air 
which  covers  the  inner  surface  of  the  membrana  tympani 
would,  no  doubt,  have  an  injurious  efiect  upon  this  mem- 
brane ;  this  efiect  would  be  mitigated  by  the  addition  of 
another  cavity,  adding  its  capacity  to  that  of  the  tympanum 
properly  so  called  ;  thus  those  animals  which  are  exposed  to 
sudden  and  considerable  changes  of  atmospheric  pressure,  as 
birds  which  fly  very  high,  have  their  mastoid  cells  more  fully 
developed  than  is  the  case  with  other  animals,  these  cells 
even  communicating  with  other  supernumerary  bony  cavities. 

The  Eustachian  tube,  which  is  situated  in  front  of  the 
middle  chamber  of  the  ear,  that  is,  facing  the  mastoid  cells, 
is  a  long  tube  extending  from  the  tympanic  chamber  to  the 
pharynx,  and  thus  forming  a  means  of  communication  be- 


420  ORG  Ays  OF  THE  SENSES. 

tween  these  two  cavities.  Many  suggestions  have  been  made 
as  to  the  probable  use  of  this  tube :  some  have  supposed  that 
it  is  intended  to  enable  us  to  hear  our  own  voice ;  the  bones 
of  the  head,  however,  serve  to  propagate  this  sound,  and 
besides,  in  its  normal  condition,  the  tube  is  closed  ;  if,  by  any 
cause,  it  is  opened  for  any  length  of  time,  the  person  hears, 
not  only  his  own  voice,  but  every  sound  produced  in  the 
upper  part  of  the  body,  such  as  the  sound  of  the  breathing, 
the  movements  of  the  velum  of  the  palate,  of  the  tongue, 
etc.;  it  has  been  observed,  in  some  cases  of  this  kind,  that 
patients  whose  attention  was  thus  constantly  directed  to  the 
various  phenomena  of  the  organism  have  at  length  become 
hypochondriacs,  an  effect  which  is  generally  produced  by 
paying  too  much  attention  to  the  facts  of  our  own  internal 
organic  existence  (see  p.  56). 

The  Eustachian  tube  is  then  normally  closed  by  means  of 
the  juxtaposition  of  its  walls,  and  opens  only  when  some 
special  organ  separates  these,  by  acting  on  the  membran- 
ous and  movable  outer  wall,  and  drawing  it  away  from 
the  other,  which  is  cartilaginous  and  quite  stationary.  This 
office  is  performed  by  the  circumflexus  or  tensor  palat%  or 
muscle  of  the  velum  of  the  palate,  and  the  effect  of  the 
opening  thus  made  is  to  bring  the  air  of  the  drum  into  com- 
munication with  that  of  the  nasal  chambers,  that  is  to  say, 
the  external  air.  The  muscles  of  the  velum  of  the  palate, 
however,  contract  only  during  the  movements  of  deglutition ; 
the  act  of  swallowing  cannot  take  place  when  there  is 
nothing  to  swallow,  and  requires,  at  least,  a  few  drops  of 
saliva.  We  return,  therefore,  to  what  we  have  already  said 
on  the  subject  of  salivation  and  deglutition,  when  we  pointed 
out  that  the  first  of  these  functions  is  closely  connected 
with  the  normal  operation  of  the  sense  of  hearing ;  and  also 
observed  that  the  secretion  of  the  saliva,  which  is  almost 
useless  in  the  carnivorous  animals,  as  regards  digestion,  is 
chiefly  connected  with  the  intermittent  movements  of  de- 
glutition, which  may  be  compared  to  the  winking  of  the  eyes ' 
and  are  intended  to  effect  the  opening  of  the  Eustachian 
tube  (see  pp.  222  and  226).  This  is  why  we  make  similar 
movements  of  deglutition,  even  when  asleep,  and  especially 
in  ascending  great  heights,  because,  beside  the  variations  in 
the  exterior  air  which  render  a  restoration  of  equilibrium 
necessary,  the  gaseous  exchanges  of  the  blood  have  the 
effect  of  varying  the  tension  of  the  interior  air ;  these  ex- 
changes  are  sometimes  very   sudden   and   of  considerable 


SENSE  OF  HEARING.  421 

amount,  as  we  saw  in  regard  to  the  stomach  and  the  digestive 
tract.  In  our  study  of  deglutition  we  made  use  of  this 
special  and  intermittent  working  of  the  Eustachian  tube  for 
the  purpose  of  demonstrating  the  strict  occlusion  of  the 
naso-plyiryngeal  orifice ;  and  then  observed  that  the  hearing  is 
obstructed  (on  account  of  the  rarefaction  of  the  air  in  the 
tympanic  cavity),  if  one  or  more  deglutitions  are  performed 
with  the  nostrils  closed ;  and  showed  the  necessity  of  degluti- 
tion performed  with  the  nostrils  open  in  order  to  restore  the 
sense  of  hearing  to  its  natural  state  (see  p.  226). 

The  tympanic  cavity  is  crossed  by  a  nerve  (the  chorda 
tympani)  which  leads  to  the  salivary  glands,  and  whose 
function  consists  of  exciting  the  secretion  of  saliva ;  so  cer- 
tain sounds,  especially  sharp  ones,  cause  an  abundant  secre- 
tion of  saliva,  no  doubt  by  means  of  their  action  on  the 
chorda  tympani  through  the  medium  of  the  membrane 
against  which  its  nerve  fibres  are  applied ;  at  all  events,  we 
cannot  avoid  associating  this  anatomical  fact  of  the  passage 
of  the  nerve  of  the  salivary  secretion  in  the  cavity  of  the 
tympanum,  with  the  physiological  fact  which  we  have  just 
been  studying,  namely,  the  essential  connection  between  the 
secretion  of  the  saliva  and  deglutition  with  the  opening  of 
the  Eustachian  tube,  and,  consequently,  with  the  keeping  up 
of  the  normal  pressure  iii  the  cavity  of  the  tympanum.  This 
relation  between  the  middle  chamber  of  the  ear  and  the 
pharynx  is  made  plain  by  the  study  of  embryology :  in  the 
fcetus  these  parts  are  confounded  together  in  the  first  pha^ 
ryngeal  cleft,  and  the  Eustachian  tube  is  the  remnant  of  this 
foetal  communication  (see  p.  405,  l^hysiology  of  the  Chorda 
Tympani), 

C.  Internal  ear. 

The  vibrations  reach  the  fluid  of  the  labyrinth  either 
through  the  columella  cochlecB  (chain  of  small  bones),  this 
being  the  usual  means  of  communication,  or  by  the  bones  of 
the  head,  especially  the  walls  of  the  external  and  the  middle 
ear ;  the  latter  is  the  case  with  persons  who,  although  they 
have  lost  the  chain  of  small  bones,  are  yet  not  completely 
deaf.  The  fluid  of  the  labyrinth  then  communicates  these 
vibrations  to  the  various  terminal  organs  of  the  auditory 
nerve  which  are  situated  in  the  vestibular  sacks  (utricula 
and  saccula),  in  the  semicircular  canals  (ampullae  and 
crest),  and  in  the  cochlea  (spiral  lamina  with  the  organ 
of  Corti).    Nothing,  however,  is  yet  positively  known  as  to 


422  ORGANS  OF  THE  SENSES. 

the  functions  of  these  various  parts  of  the  internal  ear.  It 
has  been  remarked  that  the  cochlea  appears  to  be  necessary 
to  animals  that  hear  by  means  of  vibrations  of  air,  and  that,  on 
the  other  hand,  a  sonorous  larynx,  which  is  capable  of  emit- 
ting musical  sounds,  is  generally  found  to  exist  with  it,  while 
also  accompanied  by  a  sensibility  in  the  animal  to  musical 
sounds :  it  thus  appears  to  be  the  chief  organ  of  musical 
perception,  and  the  calculation  which  has  been  made  of  the 
number  of  elements  in  the  organ  of  Corti,  compared  with 
the  scale  of  musical  notes,  seems  to  confirm  this  view.  It 
has  also  been  suggested  that  the  vestibular  chamber  may 
possess  the  power  of  judging  more,  especially  of  the  intensity 
of  notes,  and  even  of  sounds,  and  that  the  three  semicircu- 
lar canals  may,  by  means  of  their  triple  arrangement  of 
position,  horizontal  and  transverse,  vertical  and  longitudinal, 
and  horizontal,  have  the  faculty  of  judging  of  the  direction 
of  sounds ;  we  have,  however,  already  seen  that  the  pinna  of 
the  ear  has  also  the  property  of  defining  the  direction  of 
sounds. 

Whatever  be  the  special  function  of  each  part  of  the  inter- 
nal ear,  the  shock  upon  the  terminal  organs  of  the  nerves 
always  enables  us  to  distinguish  several  special  conditions  in 
the  sound  waves,  which  the  science  of  physics  shows  to  be 
the  cause  of  the  difference  in  sounds.  The  fulness  of  these 
vibrations  is  what  constitutes  the  force  or  intensity  of  sounds, 
while  their  rapidity,  or  number  in  a  certain  space  of  time, 
constitutes  the  acuteness  or  gravity  of  sounds,  and  enables  us 
to  distinguish  the  sounds  in  a  perfect  scale  from  the  lowest 
(32  vibrations  in  a  second)  up  to  the  highest  (76,000  vibra- 
tions in  a  second).  Finally,  we  distinguish  in  sounds  a 
special  quality  called  their  tone;  this  is  more  difficult  to 
define,  but  appears  to  consist  of  the  sound  resulting  from  the 
combination  of  several  notes,  whose  tone  is  different,  accord- 
ing to  the  varieties  of  the  combination.  (See  Phonation,  p. 
359.)  Habit  certainly  enables  us  to  judge  of  the  nature  of 
the  vibrating  body  by  its  tone,  which  constitutes  what  might 
be  called,  in  a  physiological  point  of  view,  the  savour  of  a 
sound ;  by  this  we  recognize  the  voice  of  a  person,  judge  of 
the  sex  by  the  voice,  and  even  judge  of  the  sentiments  of  the 
speaker ;  in  all  these  cases,  although  the  sounds  may  be  of 
the  same  intensity  and  pitch,  they  are  produced  by  .diflTerent 
combinations  of  the  same  simple  sounds';  the  waves  produced 
have,  therefore,  a  different  form,  and  in  judging  of  the  tone 
of  a  note,  we  may  be  said  to  judge  of  the/orm  of  the  vibra- 


SENSE  OF  SIGHT.  423 

tions.  No  doubt  this  faculty  which  the  organ  of  hearing 
possesses  for  judging  of  such  different  quaUties  (fulness^ 
rajnditi/,  and  form^  or  combinations  of  the  sound  waves), 
renders  necessary  that  remarkable  complication  of  structure 
in  the  internal  ear  which  will  long  continue  to  baffle  physio- 
logists. According  to  Flourens,  the  semicirmdar  canals 
have  great  influence  on  the  equilibration  of  the  animal.  This 
physiologist  discovered  that  injury  to  these  canals  produces 
rotatory  movements.  Vulpian  has  made  similar  experiments 
on  a  pigeon,  and  shown  that  rotatory,  rolling,  or  filling  move- 
ments are  produced,  according  as  the  horizontal  canal,  the 
anterior  vertical  canal,  or  the  posterior  vertical  canal  is  de- 
stroyed. These  effects  are,  however,  caused  rather  by  a 
vertigo,  and  are  no  proof  that  the  semicircular  canals  govern 
the  equilibrium  and  the  co-ordination  of  movements.  It  may 
be  asked,  finally,  whether  the  phenomena  observed  in  these 
experiments  are  really  owing  to  lesions  of  the  semicircular 
canals,  and  not  to  that  of  the  adjacent  parts.  Bottcher  made 
the  experiment  of  carefully  detaching  the  semicircular  canals 
in  a  frog,  and  succeeded  in  destroying  them  without  injuring 
any  other  part  of  the  labyrinth  or  of  the  encephalon,  and  he 
never  found  in  the  batrachians  this  operation  followed  by  any 
difficulty  in  walking  or  standing.  This  effect  is  produced 
only  when  the  lesion  is  deep-seated.  We  may  conclude  from 
this  that  the  semicircular  canals  really  form  an  organ  of 
hearing,  and  not  an  organ  which  governs  the  equilibrium  of 
walking  and  standing.     (Bottcher, "  Medic.  Zeitschr.,"  1872.) 

V.   The  Sense  of  Sight. 

The  sense  of  sight  enables  us  to  judge  of  the  luminous 
properties  of  the  objects  by  which  we  are  surrounded,  and, 
consequently,  of  their  color,  their  form,  and  their  position. 
The  organ  of  sight  (the  eye  )  is  essentially  composed,  1,  of  a 
n.embrane  (the  retina),  connected  with  the  nerve  termina- 
tions, and  upon  wliich  the  impressions  of  the  luminous  rays 
are  made ;  2,  of  a  dioptrical  organ  intended  to  collect  and 
condense  the  rays  of  light  upon  the  membrane  just  men- 
tioned, where  they  represent  in  miniature  external  objects,  as 
on  a  screen  in  a  dark  room ;  3,  of  m^embranes,  attached  to 
these  two  organs,  for  the  purpose  of  securing  and  modifying 
their  functions.  These  different  parts  (Fig.  112)  are  con- 
nected like  the  other  organs  of  the  senses,  in  a  physiological 
point  of  view,  with  the  study  of  the  surfaces  of  the  organism, 


424         ORGANS  OF  TEE  SENSES. 

which  (with  the  exception  of  the  nervous  portions)  are  formed 
in  a  great  measure  in  the  embryo,  by  deep  and  extremely 
complicated  growths  of  the  external  integument.    To  the 


Fig.  111. —The  globe  of  the  eye  (vertical  section).* 

eyeball  or  globe  of  the  eye  thus  constituted,  accessory  organs 
are  attached,  intended  either  to  move  it  (muscles  of  the  eye), 
or  to  protect  it  from  external  injury  (eyelids  and  lachrymal 
system). 

We  shall  successively  consider:  — 

1.  Physical  dioptric  apparatus. 

2.  Accessory  membranes  which  maintain  and  modify  its 
function. 

8.  Sensitive  membrane  or  retina, 
4.  Appendages  of  the  eye. 

4.1.  The  dioptrical  apparatus, 

A.  Media  of  the  ^ye. — The  dioptrical  apparatus  consists 
of  all  the  transparent  media  through  which  the  rays  of  light 
pass  in  order  to  reach  the  sensitive  membrane  situated  at  the 
bottom,  or  fundus,  of  the  eye ;  these  are,  beginning  in  front, 
the  cornea^  the  aqueous  humor,  the  crystalline  lens^  and  the 
vitreous  humor ;  the  cornea,  which,  in  an  anatomical  point 
of  view,  forms  a  part  of  the  covering  of  the  eye,  in  a  2>hysio- 
logical  point  of  view  constitutes  one  of  these  media. 

*  1,  Sclerotic.  2,  Choroid.  3,  Retina.  4,  Crystalline  lens.  5,  Hyaloid 
membrane.  6,  Cornea.  7,  Iris.  8,  Vitreous  body.  (J.  C.  Dalton,  "Human 
Physiology.") 


SENSE  OF  SIGHT. 


425 


The  transparent  cornea  is  formed  of  a  basement  membrane 
of  collagenous  tissue  (see  Fig.  23,  p.  96),  covered,  both  in  front 
and  behind,  with  an  epithelial  layer ;  that  of  the  posterior  sur- 
face is  simple  {memhrane  of  Demours  or  of  Descem.et) ;  that 
of  the  anterior  surface  resembles  the  epithelium  of  the  con- 
junctival mucous  layer, which  is  itself  continuous  with  the  skin 
and  the  epidermis ;  thus  superficial  diseases  of  the  cornea  are 
closely  connected  with  diseases  of  the  skin  or  epidermis.  The 
aqueous  or  watery  humor  is  contained  in  the  anterior  cham- 
ber (where  we  shall  presently  study  an  appendage  of  the 
choroid,  called  the  iris)^  between  the  posterior  surface  of  the 
coraea,  and  the  anterior  surface  of  the  crystalline  lens ;  this 
fluid  closely  resembles  water,  containing  in  solution  a  small 
quantity  of  albumen  and  salts,  and  is  secreted  by  the  mcm- 
brane  of  Demours  {membrane  of  the  aqueous  humor). 

The  crystalline  lens  consists  of  an  exterior  membrane, 
called  the  capsule  of  the  crystalline  le?is,  and  an  inner  sub- 
stance, called  the  body  of  the  crystalline.  The  capsule  is  an 
amorphous  and  very  elastic  tissue ;  if  an  incision  is  made  into 
its  substance,  it  retracts  and  exj3els  its  contents  (as  in  the 
operation  for  cataract) ;  its  whole  inner  surfece  is  cov- 
ered with  cells,  from  which  the  con- 
tents, or  body  of  the  crystalline  lens 
may  be  reproduced.  This  body^  in- 
deed, is  formed  of  prismatic  elements, 
arranged  regularly  in  concentric 
layers  (Fig.  112),  and  which  are  pro- 
duced by  the  metamorphosis  of  cells; 
the  study  of  embryology  shows  the 
germ  from  which  the  crystalline  pro- 
ceeds to  be  an  offslioot  from  the  epi- 
dermis (Fig.  113),  which,  finally, 
becomes  detached  and  remains  alone 
in  the  centre  of  the  eyeball  or  ocular 
globe.  The  layer  of  cells  lining  the  inner  surface  of  the  cap- 
sule thus  corresponds  to  the  layer  of  Mali)ighi  in  the  skin : 
the  crystalline  lens  is  developed  by  means  of  tliis  layer,  iu 
which  are  constantly  found  the  zones  of  young  cells  in  the 
course  of  transformation  into  prisms. 


Fi£ 


.  112.  — Disposition  of 
le  fibres  of  tlie  leus.* 


*  This  figure  shows  the  regular  disposition  of  the  prisms  of  the  crystalline 
lens,  the  extremities  of  which  are  joined  together  on  both  surfaces,  the  point  at 
whicli  thev  meet  fonning  a  sort  of  three-cornered  star ;  thus  a  lens  which  has 
been  hardened,  either  by  the  effect  of  heat  or  of  chemical  reagents,  generally 
cracks  in  this  stellate  form,  corresponding  with  the  lines  shown  above. 


426  ORGANS  OF  THE  SENSES. 

The  vitreous  humor  or  hyaloid  memhrane  is  composed  of 
collagenous  tissue,  and  resembles  the  gelatine  of  Wharton, 
especially  in  young  subjects ;  it  is  contained  in  a  very  thin 
and  transparent  sack,  called  the  hyaloid  memhrane. 


Fig.  113. — Development  of  the  crystalline  lens  (Remak).* 

B.  Refraction.  —  This  group  of  media  forms,  in  a  physical 
point  of  view,  a  series  of  three  lenses,  differing  greatly  from 
each  other:  the  firsts  consisting  of  the  cornea  and  the  aqueous 
humor^  is  a  convexo-concave  lens,  and  is  extremely  compli- 
cated on  account  of  the  various  layers  of  which  the  cornea 
is  composed.  The  second,  or  crystalline,  is  a  hi-convex  lens, 
the  anterior  surface  of  which  is  more  curved  than  the  back ; 
this,  too,  is  very  complicated,  its  concentric  layers  increas- 
ing in  density  from  the  periphery  to  the  centre.  Finally,  in 
the  third  place,  the  vitreous  body  consists  of  a  concavo-con- 
vex lens,  being  hollowed  out  in  front  for  the  reception  of  the 
crystalline  lens.  Immediately  behind  this  latter  lens  is  found 
a  membrane  which  is  sensitive  to  light  and  which  is  called  the 
retina. 

Let  us  suppose  for  the  sake  of  simplicity  that,  instead  of 
these  three  lenses,  we  have  a  single  lens  of  the  same  total 
converging  power,  and  we  shall  then  easily  understand  the 
final  result  of  the  progress  of  the  rays  of  light.  The  whole 
system,  in  short,  may  be  represented  by  a  lens  formed  of  a 
substance  whose  index  of  refraction  is  from  1.39  to  1.40, 
and  whose  focal  distance  is  17  mm.,  0.48.  The  luminous  rays, 
from  a  given  point  outside,  diverge  as  they  fall  upon  the 

*  A,  B,  C  mark  the  different  degrees  of  invagination  or  separation  of  the 
pouch  from  which  the  crystalline  lens  is  formed.  1,  Epidermic  fold.  2,  Thick- 
ening of  this  fold,  pouch  of  the  separated  crystalline  (at  B).  3,  Crystalline 
fossette,  which  will  afterwards  appear  as  the  centre  of  the  lens.  4,  Primitive 
ocular  vesicle  (nerve  pouch  arising  from  the  encephalic  centre),  the  forepart  of 
which  has  a  depression  for  the  lens.  7,  Cavitv  formed  by  the  compression  of  the 
ocular  vesicle,  and  which  is  to  be  occupied  by  the  vitreous  body.  6,  Point  at 
which  the  lens  is  detached  from  the  epidermic  fold. 


SENSE   OF  SIGHT. 


427 


cornea,  converging  again  after  passing  through  this  dioptrical 
organ,  and  uniting  in  a  point  which,  in  the  normal  state,  and 
under  circumstances  which  we  will  mention,  is  situated 
directly  on  the  retina:  it  is  here  that  extenial  objects  are 
represented  in  smaller  dimensions.  If  the  convergence,  how- 
ever, does  not  take  place  exactly  on  the  retina,  but  rather  in 
front  or  behind  it,  we  can  easily  understand  that  every  point 
of  the  object  ])resented  to  the  eye  will  be  represented  on  the 
membrane,  not  as  a  point,  but  as  a  small  circle,  which  corre- 
sponds to  the  plan  of  section  by  the  retina  of  the  converging 
cone,  which  these  rays  form  before  their  union,  or  of  the 
diverging  cone  which  they  form  after  their  union  (Fig.  114). 
In  order  to  make  this  perfectly  plain,  let  us  give  the  name 
of  objective  cone  to  the  cone  of  luminous  rays  which,  pro- 
ceeding from  the  luminous  point,  diverge  as  they  fall  upon 


Fig.  114.  —  Ocular  and  objective  cones.* 

the  cornea,  and  that  of  ocular  cone  to  the  cone  which  repre- 
sents these  rays  after  undergoing  the  converging  influence  of 
the  ocular  lens  (Fig.  114)  :  the  slightest  familiarity  with 
optics  will  show  us  that  if  the  rays  of  light  come  to  us  from 
a  great  distance,  as  from  a  star,  the  objective  cone  will  attain 


*  A,  B,  The  luminous  points  under  consideration,  c,  c,  Cornea.  D  D,  Iris. 
E  E.  Lens. 

At  first  the  luminous  rays  which  set  out  from  the  points  A  or  B  are  bent  hy 
tlie  cornea  C  C  and  by  the  watery  humor  contained  between  this  membrane  and 
the  crystalline,  that  is,  they  are  brought  near  to  the  median  ray  which  travels  on 
a  line  parallel  with  the  axis.  A  second  refraction  takes  place  in  the  lens,  and 
the  final  result  appears  in  the  form  of  ocular  cones,  the  smnmit  of  which  is  at 
a  and  6,  or  exactly  on  the  retina:  but  we  also  see  that  if  the  retina,  instead  of 
exactl}'  corresponding  with  the  summit  of  the  ocular  cones,  intersected  them 
either  farther  fonvard  (at  H)  or  backward  (at  G),  the  image  formed  upon 
this  membrane  would  no  longer  be  a  point,  but  a  small  circle  {circle  of 
diffusion). 


428  ORGANS  OF  TEE  SENSES. 

its  greatest  length,  while  the  ocular  cone  will  become  as 
short  as  it  is  possible  for  it  to  be.  If,  on  the  other  hand, 
the  luminous  rays  proceed  from  an  object  very  near  the 
eye,  the  objective  cone  will  be  very  short,  while  the  ocular 
cone  which  it  produces  in  the  eye  Avill  be  much  longer 
than  in  the  former  case.  We  see,  therefore,  that  it  is  only 
when  at  a  certain  distance  from  the  luminous  object  that  the 
ocular  cone  is  of  such  a  length  that  its  summit  falls  exactly 
on  the  retina ;  in  all  other  cases,  the  luminous  point  being 
farther  from,  or  nearer  to,  the  eye,  the  ocular  cone  produced 
will  be  either  too  long  or  too  short,  and  its  summit  will  con- 
sequently be  either  before  or  behind  the  retina :  in  short,  the 
luminous  point  will  be  represented  on  the  retina,  not  as  a 
point,  but  as  a  small  circle,  called  the  circle  of  diffusion^  and 
the  image  resulting  from  it  will  be  confused. 

What  would  happen  in  a  physical  organ  such  as  we  have 
described  does  not,  however,  take  place  in  the  eye,  in  its 
normal  state.  Whatever  (within  certain  limits)  be  the  dis- 
tance of  the  luminous  point,  we  have  the  power  of  bringing 
the  summit  of  the  ocular  cone  produced  by  the  rays  of  light 
proceeding  from  it,  directly  upon  the  retina:  a  man  can 
alternately  look  at,  and  see  with  nearly  equal  distinctness,  a 
star  and  the  end  of  his  nose.  In  short,  we  have  the  power  of 
adapting  or  accommodating  our  eye  to  different  distances. 

C.  Adaptation  or  Accommodation.  —  The  method  ofadap- 
tation  or  the  exact  coincidence  of  the  summit  of  the  ocidar  cone 
with  the  retina^  has  been  only  recently  and  exactly  defined.  For 
a  long  time  the  existence  of  this  accommodation  was  denied. 
It  may,  however,  be  proved  in  several  ways.  If,  for  instance, 
we  hold  up  two  fingers,  one  behind  the  other,  at  a  certain 
distance,  and  fix  our  attention  on  one,  we  shall  find  that  we 
see  distinctly  only  this  one,  the  eye  being  adapted  to  see  only 
one  and  not  the  other,  which  appears  vaguely  defined ;  this 
is  because,  at  this  moment,  one  of  the  two  fingers  is  distinctly 
painted  on  the  retina,  while  the  other  only  produces  circles 
of  diffusion  upon  it.  This  fact  is  still  more  clearly  demon- 
strated by  a  celebrated  experiment  made  by  Scheiner,  and 
which  consists  in  placing  before  the  eye  a  card  in  which  two 
small  holes  are  pierced  near  each  other  (Mm  Nn,  Fig.  115), 
and  then  looking  through  them  at  two  luminous  points  (the 
heads  of  two  pins,  for  instance)  placed  one  befor^  the  other, 
at  a  certain  distance  (as  with  the  two  fingers  in  the  fore- 
going experiment)  :  if  we  look  at  one  of  these  points  fixedly^ 
we  shall  see  the  latter  double.    The  reason  of  this  is  owing  to 


SENSE  OF  SIGHT. 


429 


the  fact  that,  when  we  look  at  the  luminous  point  a,  through 
the  two  openings  Mm  and  Nn  (Fig.  115),  a  phenomenon  of 
adaptation  takes  place  in  the  eye,  by  means  of  which  the 
summit  of  the  ocular  cone  falls  upon  the  retina ;  the  summits 
of  the  two  partial  cones  passing  through  the  two  openings 
are  joined  together  in  one  (in  a),  these  two  cones  making  a 
part  of  the  total  cone  which  would  be  produced  if  the  lumi- 
nous point  were  looked  at  with  the  naked  eye ;  this  is  the  case, 


r:?:.v::/i?-?ssi«»  o 


Fig.  115.  —Experiment  by  Scheiner.* 

however,  only  with  regard  to  the  point  a ;  the  objective  cone 
of  the  point  5,  being  longer,  its  ocular  cone  will  be  shorter; 
and  the  summit,  consequently,  will  be  in  front  of  the  retina, 
and  can  strike  this  membrane  only  by  diverging  after  bring- 
ing about  the  intersection  of  its  rays :  if  then,  as  in  this  ex- 
periment, the  cone  be  divided  in  two  by  looking  through  two 
holes,  the  object  J,  which  is  not  looked  at,  will  be  projected  as 
two  distinct  cones  (and  will  be  seen  double)  ;  since  they  strike 
the  retina,  not  at  the  point  of  their  common  summit  {b')^  but 
farther  back,  where  they  are  again  separated  (5",  b").  The 
eye,  in  this  case,  is  evidently  so  adapted  as  to  see  a  and  not 
b  :  but  if  b  be  looked  at  attentively,  a,  in  its  turn,  will  appear 
double. 

These  facts  are  sufficient  to  prove  that  we  possess  the 
power  of  adapting  or  accommodating  our  sight  to  different 
distances,  and  this  is  true  up  to  a  certain  point,  whatever  be 
the  distance;  thus  we  can  see  objects  which  are  placed  at  an 


*  A  B,  Diaphragm  with  two  ai)ertures  (Mm  and  Nn). 

a,  Point  for  which  the  eye  is  adapted,  and  the  image  of  which  appears  at  a 
(on  the  retuia). . 

b.  Point  for  which  the  eye  is  not  adapted;  the  luminous  rays  proceeding  from 
it  meet  at  1/  (in  front  of  the  retina),  diverge  again,  and  meet  the  retina  at  fr"  V^, 
causing  the  point  b  to  appear  double. 


430 


ORGANS  OF  THE  SENSES. 


indefinite  distance,  and  can  see  clearly  those  at  a  distance  of 
25  centimetres.  This  is  the  distance,  in  fact,  at  which  we 
receive  the  greatest  quantity  of  light,  and  the  faculty  of 
adaptation  usually  lies  between  an  indefinite  distance  and  one 
of  25  centimetres. 

There  are,  however,  sometimes,  great  differences  in  this 
phenomenon ;  the  limits  which  we  have  mentioned  are  those 


Fig.  116.— Hypermetropic  eye  and  myopic  eye  (far-sighted  and  near-sighted  eye).» 

belonging  to  eyes  in  the  normal  condition,  which  are  called 
emmetropic.  The  ocular  media  of  some  persons,  however, 
have  so  little  converging  power  that,  whatever  be  the  length 
of  the  objective  cone,  the  ocular  cone  is  never  sufficiently 
short  to  allow  its  summit  to  fall  upon  the  retina ;  even  when 
the  luminous  point  is  at  an  infinite  distance,  its  image  goes 
beyond  the  retina;  such  persons  are  called  hypermetropic,  in 
other  words,  the  object  would  have  to  be  placed  at  distance 
more  than  infinite  before  the  summit  of  its  ocular  cone  could 


*  1,  Hypermetropic  Eye.  —  The  luminous  rays  ari\ang  from  an  infinite  dis- 
tance (parallels)  produce  an  ocular  cone,  the  summit  of  which  falls  beyond  the 
retina  (at  a),  either  because  the  cone  is  too  long  (lack  of  converging  power  in 
the  media  oi  the  eye),  or  because  the  retina  is  too  far  forward  (the  eye  being  too 
short). 

2,  Myopic  Eye.  —  The  luminous  rays  from  an  infinite  distance  (parallels) 
produce  an  ocular  cone,  the  summit  of  which  falls  in  front  of  the  retina  fat  6), 
either  because  this  cone  is  too  short  (excess  of  converging  power  in  the  media), 
or  because  the  retina  is  placed  too  far  back  (the  eye  being  too  long).  Donders's 
researches  seem  to  show  that  short-sightedness  is*  owing  to  this  latter  cause,  as 
is  well  shown  in  the  figure :  the  ocular  globe  being  greatly  elongated  from  back 
to  front). 


SENSE  OF  SIGHT.  431 

fall  upon  the  retina  (Fig.  116,  1)  :  such  eyes  are  called  hyper- 
metropic, and  this  want  of  convergence  (or  shortness  of 
the  ocular  cone)  constitutes  hypermetropia.  On  the  other 
liand,  the  ocular  medium  of  some  persons  has  so  much  con- 
verging power  that  the  ocular  cone  is  always  too  short,  and, 
in  order  to  see  objects  distinctly,  they  are  obliged  to  place 
them  very  near  the  eye ;  so  that,  as  the  cone  lengthens,  its 
summit  may  fall  upon  the  sensitive  membrane:  this  is  the 
case  with  short-sighted  persons  (Fig.  116,  2),  and  this  short- 
ness of  the  ocular  cone  constitutes  what  is  called  myopia} 

We  see  that  hypermetropia  and  myopia  are  two  opposite 
conditions ;  in  the  former,  the  eye,  when  in  the  state  of  repose, 
and  making  no  eflfort  to  adapt  itself  to  objects,  sees  only  those 
which  are  at  the  greatest  possible  distance  from  it ;  while  in 
the  latter,  under  similar  circumstances,  it  sees  those  only 
which  are  close  at  hand.  Another  condition  of  the  eye  which 
is  frequently  mistaken  for  hypermetropia  is  that  called  pres- 
byopia ;  this  derangement  of  the  functions  of  the  ocular 
medium  consists  in  a  diminution  of  the  power  of  adaptation 
which  can  be  no  longer  exercised  on  objects  near  the  eye ; 
this  is  generally  found  to  be  the  case  as  persons  advance  in 
age.  In  hypermetropia  the  ocular  cone  is  always  too  long  ^ 
in  myopia,  it  is  always  too  short ;  in  both  cases,  however,  the 
power  exists  of  modifying  the  cone,  by  adaptation,  especially 
of  shortening  it,  as  we  shall  presently  see.  A  far-sighted 
person,  on  the  contrary,  or  one  suffering  from  presbyopia,  has 
scarcely  any  power  of  modifying  the  cone  in  order  to  see 
objects  near  the  eye ;  thus  we  see  that  if  a  nonnal  eye  may 
become  presbyopic,  a  hypermetropic  or  a  short-sighted  eye 
may  do  so  likewise,  and  that  short-sightedness  and  presbyobia 
may  exist  together. 

Means  of  remedying  these  defects  of  sight  have,  however, 
been  found  in  optics :  for  the  purpose  of  modifying  an  ocular 
cone  which  is  too  long  or  short,  either  a  concave  or  a  convex 
glass  is  placed  before  the  eye.  If  we  have  the  slightest 
knowledge  of  physics,  we  shall  be  able  to  understand  that  a 
concave  or  diverging  glass,  lengthens  the  ocular  cone  by 
diminishing  the  converging  power  of  the  eye :  short-sighted 
persons,  for  this  reason,  use  concave  glasses.  On  the  other 
hand,  a  convex  or  converging  glass  shortens  the  ocular  cone 

^  See,  in  the  "  Nouv.  Diet,  de  Med.  et  de  Chirur.  Prat.," 
articles  by  Liebreich  and  Javal:  "  Accommodation,  Emmetropic, 
Diplopie,  Asthenopie,"  etc. 


432  ORGANS  OF  THE  SENSES. 

by  increasing  the  converging  power  of  the  eye :  liyperme- 
tropics^  therefore,  make  use  of  a  convex  glass,  for  the  purpose 
of  shortening  the  ocular  cone,  as  do  also  far-sighted  persons 
when  they  desire  to  see  objects  near  at  hand,  their  power  of 
accommodation  or  adaptation  being  insufficient  for  this  pur- 
pose. 

The  study  of  these  various  degrees  of  converging  power  in 
the  eye,  and  of  the  artificial  means  by  which  its  defects  are 
remedied,  will  enable  us  to  understand  how  accommodation  is 
effected  in  the  normal  condition.  The  use  of  glasses,  of  which 
we  have  just  spoken,  is  a  sort  of  artificial  accommodation, 
especially  in  the  case  of  far-sighted  persons.  It  is,  therefore, 
probable,  that  in  physiological  accommodation,  something 
similar  takes  place ;  in  other  words,  the  converging  power  of 
this  organ  is  modified. 

It  was  for  a  long  time  supposed  that  the  mechanism  of 
accommodation  consisted  in  a  change  in  the  form  of  the  eye, 
modifying,  not  the  ocular  cone,  but  the  position  of  the  retina; 
which  would  then  be  placed  at  the  summit  of  the  cone,  caus- 
ing the  eye,  when  looking  at  objects  at  a  distance,  to  shorten 
in  antero-posterior  diameter  under  the  influence  of  the  recti 
muscles  of  the  eye,  .and  to  lengthen  under  that  of  its  oblique 
muscles,  when  looking  at  objects  close  at  hand.  This  func- 
tion of  the  motor  muscles  of  the  eye  is,  however,  entirely 
hypothetical,  and  the  theory  is  contradicted  by  the  anatom- 
ical arrangement  of  these  muscles,  as  well  as  by  physiological 
experiments. 

It  has  been  also  supposed  that  the  crystalline  lens  can  be 
moved  backwards  or  forwards,  and  can  act  in  the  same  man- 
ner as  we  use  the  objective  in  a  microscope  when  we  desire 
to  bring  an  object  into  focus ;  a  knowledge  of  anatomy,  how- 
ever, shows  that  this  is  impossible,  and  direct  experiments 
have  shown  that  there  is  no  foundation  for  such  a  theory. 

Direct  experiment  shows  that  accommodation,  as  our  study 
of  artificial  adaptation  would  lead  us  to  suppose,  consists  in 
a  change  of  curve,  and,  consequently,  a  change  in  the  con- 
verging power  of  one  only  of  the  media  of  the  eye,  the  crystal- 
line lens.  The  experiment  is  made  by  studying  the  images 
furnished  by  the  different  surfaces  of  the  media  of  the  eye, 
these  surfaces  acting  like  mirrors.  Thus  we  may  easily  ob- 
serve that  objects  are  reflected  in  the  surface  of  the  cornea, 
as  well  as  in  the  anterior  and  posterior  surfaces  of  the  crys- 
talline lens;  so  that,  if  we  place  a  light  before  an  eye  (Fig. 
117),  we  shall  find  in  the  eye  three  images  of  the  flame :  the  two 


SENSE  OF  SIGHT.  433 

"t^nght  ones  (a  and  b)  appearing  in  the  cornea  (a),  and  in 
the  anterior  surface  of  the  crystalline  lens  (b)  (convex  mir- 
rors) ;  and  the  one  upside  down  (c),  on  the  posterior  surface 
of  the  crystalline  lens  (concave  mirror).  If  the  person  ex- 
perimented upon  be  made  to  look  fixedly  at  objects  placed 
at  different  distances,  the  only  change  in  the  three  reflections 
which  we  have  mentioned  will  be  found  to  take  place  in  that 
furnished  by  the  anterior  surface  of  the 
"ciystalline  lens  (the  reflection  b).  We 
conclude  from  this,  that  in  the  phenom- 
enon of  accommodation  the  anterior  sur- 
face of  the  crystalline  lens  alone  undergoes 
a  change ;  while,  by  measuring  the  image 
in  question,  we  find  (according  to  the 
laws  of  convex  mirrors)  that,  in  looking 
at  an  object  at  a  distance,  the  convexity 
of  the  crystalline  lens  is  diminished  (since  Fig.  117.— images  pro- 

n     t  .1     .   ai       '  •  •        •      \  duced  on  the  surfaces 

we  find  that  the  image  increases  in  size)  ;      ofthe  ocular  media  act- 
while  if,  on  the  other  hand,  the  object  is      \ps.  »» .mirroi^s  (Pur- 

^    '  -^     •    •  J  /^i      •  kiiye's  images).* 

near,  the  convexity  is  increased  (the  image 
being  then  reduced  in  size). 

Therefore,  accommodation  takes  place  by  the  modification 
of  the  crystalline  lens.  We  shall  examine  the  other  means 
by  which  the  form  of  this  lens  may  be  changed,  when  we 
come  to  the  subject  of  those  accessory  membranes,  especially 
the  choroid  and  the  iris  (the  ciliary  muscle)  which  are  in- 
tended to  assist  and  to  modify  the  working  of  the  essential 
parts  of  the  eye. 

D.  Imperfections  in  the  System  of  Ocular  Dioptrics. — Con- 
sidered as  a  physical  organ,  the  eye  is  far  from  being  perfect : 
the  various  imperfections  belonging  to  similar  physical  organs 
:ire  found  in  it,  and  are  known  under  the  name  either  of 
spherical  aberration  or  chromatic  aberration. 

The  essential  part  of  the  organ  of  the  eye  being  a  lens,  it 
so  happens  that  this  lens,  even  when  most  perfect,  does  not 
unite  exactly  at  the  same  point  all  the  rays  which,  proceed- 
ing from  the  same  luminous  source,  fall  upon  the  edges  or 
upon  the  centre  of  the  crystalline  lens.  The  focus  of  the  lens 
is  not,  therefore,  single  in  its  kind,  and  it  is  this  which  gives 
rise  to  the  aberration  of  sphericity.     We  shall  see  that  the 

*  a,  Upright  image  reflected  by  the  cornea,  ft,  Upright  image  reflected  by 
the  anterior  surface  of  the  lens,  c,  Image  upsidedown  reflected  by  the  pos- 
terior suiface  of  the  lens. 

28 


434  ORGANS  OF  THE  SENSES. 

iris,  like  the  diaphragms  of  optical  instruments,  serves  in  part 
to  remedy  this  defect. 

The  chromatic  aberration  results  from  the  unequal  refran- 
gibility  of  the  various  colored  rays  of  which  white  light  is 
composed.:  by  means  of  this,  the  eye  decomposes  the  ordinary 
light  of  the  objects  which  project  it,  and  we  see  them  more 
or  less  colored ;  the  eye,  in  short,  is  not  a  perfect  achromatic 
organ.  Habit  renders  us,  for  the  most  part,  insensible  to 
this  defect,  but  various  experiments  show  it  plainly.  We 
will  mention  only  one :  after  looking  at  the  cross-hairs  of  an 
astronomical  glass,  by  a  red  light,  we  shall  find  that,  in  order 
to  see  them  with  another  ray  of  the  spectrum  (another  color), 
the  position  of  the  ocular  or  eye-piece  must  be  changed ;  the 
eye,  when  so  adapted  as  to  see  by  the  red  light,  not  being 
adapted  to  see  perfectly  by  the  other  rays  of  the  spectrum. 

Finally,  a  certain  irregularity  of  curve  in  the  surfaces  of 
the  media  of  the  eye  constitutes  what  is  called  astigmatism. 
(or  monochromatic  aberration).  Astigmatism  is  such  a 
common  defect  in  the  refraction  of  the  eye  that  it  may  be 
said  to  be  found,  in  a  varying  degree,  in  most  persons ;  it 
does  not,  however,  usually  affect  the  sight  so  much  as  to  be 
noticed.  Astigmatism  consists  in  the  more  or  less  sensible 
curve,  from  one  meridian  to  the  other  of  the  surfaces  of 
separation  between  the  media  of  the  eye  (especially  the  curve 
of  the  interior  surface  of  the  cornea).  Let  us  suppose  a 
cornea  in  its  normal  condition  divided  into  two  halves,  fol- 
lowing the  line  of  its  vertical  axis,  the  parts  maintaining  their 
original  position  ;  the  surface  of  the  section  will  represent  a 
curve  of  a  fixed  radius;  if  the  cornea  be  divided,  following 
its  transverse  axis,  the  surface  of  the  section  will  exhibit  ex- 
actly the  same  curve  (in  a  normal,  non-astigmatic  eye) ;  in 
other  words,  both  sections  will  conform  to  a  circumference  of 
the  same  radius.  On  the  other  hand,  in  an  eye  affected  with 
astigmatism  (as  nearly  all  eyes  are)  the  radius  of  one  will  be 
shorter  than  that  of  the  other;  the  two  curves,  in  short, 
are  unequal.  It  is  easy  to  see  that  this  inequality,  if  suffi- 
ciently great,  will  interfere  with  the  course  of  the  luminous 
rays  as  they  penetrate  the  eye ;  in  fact,  if  we  suppose  that 
the  radius  of  one  circumference  is  considerably  shorter  than 
that  of  the  other,  we  shall  conclude  that  the  eye  is  short- 
sighted in  the  one  sense,  while  in  another  it  may  be  much 
less  so,  or  not  at  all,  or  even  may  be  hypermetropic.  In  order 
to  remedy  this  defect  in  the  refraction  of  the  eye,  it  is  plainly 


K 


SENSE  OF  SIGHT.  435 

sufficient  to  make  the  luminous  rays  pass  through  a  lens  cut 
in  such  a  manner  as  to  restore  the  equilibrium  between  the 
two  meridians,  so  that  the  rays,  after  passing  through  this 
lens  and  through  the  medium  of  the  cornea,  follow  the  same 
direction  as  the  rays  which  pass  through  an  ordinary  cornea. 
The  surface  of  the  glasses  used  for  this  purpose  is  cylindrical, 
instead  of  being  spherical,  and  they  are  arranged  in  such  a 
manner  that  the  convergence  which  they  produce  on  a  single 
plane  corresponds  exactly  with  the  plane  of  that  meridian 
according  to  which  the  surface  of  the  cornea  of  the  eye  is  in- 
sufficiently convex :  in  this  way,  such  want  of  convexity  is 
remedied. 

II.  Enveloping  membranes  of  the  eye. 

Beginning  from  the  outside,  and  going  towards  the  centre 
of  the  eye,  we  find  that  there  are  three  envelopes  of  the  eye, 
the  white  of  the  eye.,  the  choroid.,  and  the  retina  ;  the  latter 
being  the  membrane  which  is  especially  endowed  with  sensi- 
bility. We  will  consider  the  two  first  as  protecting  envel- 
opes, intended  to  assist,  and  even  to  tnodify  the  functions  of 
the  other  and  essential  portions  of  the  eye. 

1.  The  Sclerotic.  —  The  sclerotic  coat  of  the  eye  forms, 
as  it  were,  its  skeleton.  This  membrane  is  intended  to  pre- 
serve the  form  of  the  ocular  globe,  and  into  it  the  muscles 
that  move  the  globe  are  inserted.  It  has  a  fibrous  texture  in 
man,  but  cartilaginous  and  even  bony  in  birds  and  reptiles. 
This  white  of  the  eye  in  front  undergoes  a  change ;  from 
being  white  and  opaque,  it  becomes  transparent  and  color- 
less, constituting  the  cornea^  which  we  have  already  studied. 
The  cornea  is  more  convex,  and  belongs  to  the  segment  of  a 
sphere  whose  radius  is  shorter  than  that  of  the  white  of  the 
eye,  or,  in  other  words,  of  that  of  the  other  portions  of  the 
eyeball  (Fig.  Ill,  p.  491). 

2.  The  Choroid  Tunic  or  Coat.  — The  choroid  coat  lines 
the  sclerotic  throughout,  except  where  it  joins  the  cornea, 
and  enters  the  anterior  chamber  of  the  eye,  where,  in  front 
of  the  crystalline  lens,  it  forms  a  diaphragm  called  the  iris. 
We  have,  therefore,  to  study  both  the  choroid  coat.,  properly 
so  called^  and  the  iris. 

A.  The  choroid,  properly  so  called,  is  essentially  a  vascular 
membrane ;  its  inner  surface  is  also  lined  with  a  layer  of 
pigment  cells,  of  a  regularly  hexagonal  shape ;  it  contains, 
finally,  muscular  elements,  especially  in  front.  Three  princi- 
pal functions  are,  therefore,  assigned  to  this  membrane. 


436 


ORGANS  OF  THE  SENSES. 


1.  As  a  TKiscular  organ  (having  numerous  cUiary  or 
<:horoid  arteries^  and  groups  of  veins,  forming  the  vasa  vor- 
ticosa)  its  purpose  is  to  serve  as  an  organ  of  calefaction  to 
the  nerve  membrane  beneath  it  (the  retina).  We  have  seen 
that  those  organs  which  contain  numerous  nerve  termina- 
tions, particularly  the  organs  of  the  special  senses,  usually 
have  an  abundance  of  blood  vessels,  as  we  see  in  the  papillaa 
of  the  inner  aspect  of  the  fingers,  the  olfactory  membrane, 
the  tongue,  etc. 

2.  The  pigment  of  the  inner  svrface  of  the  choroid  is  of 
great  importance  to  sight ;  the  retina  being  transparent,  the 
rays  of  light  fall  upon  the  choroid  pigment ;  the  effect  pro- 
duced is  not  yet  perfectly  understood.  It  may  be  that  this 
layer  absorbs  the  more  irritating  rays,  and  serves  as  a  reflect- 
ing mirror  to  the  others,  which  affect  the  terminal  organs  of 
the  nerve  fibres  of  the  retina ;  we  shall  find,  indeed,  that  the 
free  surface  of  the  sensory  elements  of  the  retina  is  turned 
towards  the  choroid,  and  that  these  elements  are,  undoubt- 
edly, affected  only  by  the  rays  reflected  in  this  sort  of  mirror 
(Ch.  Rouget).  This  pigment  layer  is  not  always  quite 
black.  There  are  various  shades  in  different  animals ;  thus, 
in  the  ox,  it  exhibits  metallic  reflections  exactly  resembling 
the  surface  of  a  mirror..  This  pigment  layer,  which  is  so 
dark  and  opaque  in  other  parts,  is,  perhaps,  like  the  black 
covering  with  which  the  inner  surface  of  a  camera  obscura 
is  lined,  to  prevent  the  irregular  reverberation  in  all  direc- 
tions of  the  rays  of  light,  and  thus  to  promote  the  distinct- 
ness of  the  sight ;  animals  which  have  no  choroid  pigment 
(albinos)  are  scarcely  able  to  endure  a  strong  light  {helio^ 
phobia).  The  choroid  pigment  is,  certainly,  a  valuable  aid  to 
sight,  and  the  weakening  of  the  sight  in  old  age  is  partly 
owing  to  a  loss  of  color  of  the  inner  surface  of  the  choroid. 

3.  Finally,  the  muscular  elements  of  the  choroid  {ciliary 
muscles)  which  are  developed  principally  in  its  anterior  part, 
and  joined  to  erectile  prolongations  {ciliary  process),  are 
chiefly  intended  to  act  upon  the  crystalline  lens,  and  produce 
the  changes  of  form  which  we  have  studied  in  regard  to 
accommodation ;  great  differences  of  opinion,  however,  prevail 
as  to  the  mechanism  by  which  the  muscular  action  affects  the 
lens  (Fig.  118).  The  ciliary  muscle  is  composed  of  longitur- 
dinal  and  circular  Jibres.  The  former  act  by  drawing  for- 
ward, from  a  fixed  point  at  the  junction  of  the  sclerotic  coat 
and  the  cornea  (near  the  canal  of  Schlemm,  sinus  circularis 
iridis),  the  whole  choroid  membrane,  and,  consequently,  the 


SENSE   OF  SIGHT. 


437 


vitreous  humor  and  also  the  crystalline  lens;  the  latter 
becomes  flattened  by  the  resistance  offered  to  it  by  the 
aqueous  humor,  or  else  becomes  more  convex  at  the  centre 
of  its  anterior  surface,  whilst  the  iris  opposes  a  deformation 


fC 


mil: 

f  —^  o  n  - 

»  o  g  -    g  Gr^ 
<B  »  2  3  p  s,     -^ 


2  s 

&^g§:p    i- 

"g"lir  i 

3  1  o  f^S  2.     ? 
•4  *i  fi  'i  3  a      * 

I'   «?^ 
8  -"  r^  CD  -^ 


of  the  peripheral  part  to  which  it  is  attached.  It  is  possible, 
on  the  other  hand,  that  the  circular  fibres^  in  contracting, 
press,  by  means  of  the  ciliary  process,  on  the  circumference 
of  the  crystalline  lens,  which  in  this  sense  gives  way ;  yet, 
owing  to  its  great  elasticity,  its  thickness  at  the  same  time 


438  ORGANS  OF  THE  SENSES. 

increases,  especially  in  the  central  part  of  its  anterior  surface, 
tliis  centre  being  the  only  part  that  is  free  and  susceptible  of 
deformation,  because  the  iris  prevents  any  thing  of  the  kind 
from  taking  place  in  the  periphery.  The  space  which  was 
supposed  to  exist  between  the  iris  and  the  crystalline  lens, 
and  which  was  called  the  posterior  chamber,  has  really  no 
existence,  the  iris  coming  in  immediate  contact  with  the 
entire  corresponding  surface  of  the  crystalline  lens  (Rouget). 
The  contractions  of  the  iris  may,  perhaps,  also  affect  the 
shape  of  the  lens ;  at  all  events,  the  iris  appears  to  lend  an 
important  aid  to  sight,  since  we  see  persons  who,  although 
they  possess  to  perfection  the  faculty  of  accommodation,  are 
yet  unable  to  see  clearly,  because  they  have  lost  the  power 
of  contracting  the  iris,  which  has  been  destroyed  or  injured. 

Ch.  Rouget  has  shown,  in  describing  the  i?iter7ial  or  an- 
nular ciliary  muscle,  that  this  muscle,  in  contracting,  com- 
presses theirido-choroid  venous  trunks,  forces  all  the  blood  to 
pass  through  the  ciliary  process,  and  thus  gives  rise  to  the 
erection  or  rigidity  of  these  organs ;  without  these  phenom- 
ena the  ciliary  muscles  would  have  no  action  on  the  crys- 
talline lens.  None  of  the  theories  of  accommodation  were 
able,  by  the  help  of  known  facts,  to  explain  the  direct  influ- 
ence upon  the  crystalline  lens :  this  effect  is  produced  by  the 
annular  ciliary  muscle ;  the  first  contractions  of  this  muscle 
obstruct  the  flow  of  blood  through  the  veins,  and  cause  the 
erection  of  the  ciliary  process ;  and,  while  in  this  state,  these 
organs  become  fitted  to  transmit  to  the  crystalline  lens,  in  a 
modified  form,  the  pressure  exercised  by  the  ciliary  muscle. 

We  see,  in  short,  that  the  contractions  of  the  anterior 
portions  of  the  choroid  coat  (ciliary  muscle)  have  the  effect 
of  producing  accommodation.  This  adaptation  is  involuntary 
and  spontaneous,  and  is  the  consequence  of  a  reflex  phenom- 
enon :  it  seems  as  if  the  retina  or  the  central  organs  of  sight, 
perceiving  the  confusion  of  the  image  produced,  reacted  upon 
the  ciliary  muscles,  thereby  causing  their  contraction.  The 
ciliary  or  ophthalmic  ganglion  was  long  considered  as  the 
centre  of  these  reflex  phenomena,  but  they  are  now  supposed 
rather  to  belong  to  the  cephalic  or  cerebral  portion  of  the 
cord  (Pons  Varolii  quadrigemina  and  corpora,  see  p.  59). 
The  muscular  fibres  of  the  choroid  tunic  are  smooth :  this 
accounts  for  a  certain  slowness  in  the  accomplishment  of  the 
process  of  accommodation. 

B.  The  iris  is  really  a  diaphragm  situated  in  the  camera 
obscura    formed    by   the    eyeball:    its   anterior  surface  is 


SENSE  OF  SIGHT.  439 

in  contact  with  the  aqueous  humor,  and  is  lined  with  a 
prolongation  of  the  membrane  of  Descemet  (of  the  posterior 
surface^  of  the  cornea,  see  Fig.  118, 13).  Its  posterior  surface, 
as  we  have  said,  is  in  close  contact  with  the  peripheral  por- 
tion of  the  anterior  convexity  of  the  crystalline  lens,  proving 
that  the  so-called  posterior  chamber  has  no  existence.  The 
periphery  is  continuous  with  the  choroid  tunic,  to  which  this 
diaphragm  forms  an  appendage ;  its  central  opening  corre- 
sponds with,  the  centre  of  the  crystalline  lens,  constituting 
what  is  called  thoi  pupil  of  the  eye. 

The  structure  of  this  membrane  is  similar  to  that  of  the 
choroid :  it  contains  a  large  number  of  vessels,  pigment  cells, 
which  also  foi*m  a  thick  layer  upon  its  deep  or  posterior  sur- 
face {uvea),  and  of  muscular  fibres.  The  latter  is  the  most 
important  element :  it  consists  of  fibres  arranged  in  a  circle 
(sphincter  of  the  pupil),  and  radiating  fibres  (dilatator 
pupillce)',^  these  fibres  appear  to  be  innervated  by  two  dif- 
ferent nerves,  the  sphincter  or  circular  fibres  by  the  motores 

'  Ch.  Rouget's  researches  do  not  confirm  the  theory  of  the 
existence  of  radiating  or  dilating  fibres  of  the  iris.  This  physi- 
ologist has  observed  that  in  the  iris  of  birds  there  are  only  muscular 
fibres,  arranged  in  a  circle,  and  which  may  produce  a  contraction 
of  the  pupil.  He  shows  that  the  radiating  bundles,  which  are  con- 
sidered as  the  dilating  muscle  of  the  pupil  in  the  mammalia  and 
in  man,  really  correspond  with  the  veins  of  the  iris  when  devoid 
of  blood.  Therefore  the  iris  is  not  in  an  active  state  when  dilated, 
as  is  the  case  when  contraction  of  the  pupil  occurs  :  the  latter 
movement  alone  is  active.  A  certain  muscular  arrangement  will 
suffice  to  explain  all  the  changes  ©f  the  pupil,  if  the  repose  of  the 
iris  ha  represented  by  the  extreme  state  of  dilatation.  There  is 
great  difficulty  in  observing  this  state  of  repose  of  the  iris:  the 
pupil  is  seldom  found  to  be  entirely  dilated,  even  after  death;  this 
is  due  to  the  fact  that  the  direct  action  of  light  (as  shown  by 
Brown-Sequard),  and  the  final  contraction  that  produces  cadaveric 
rigidity  in  the  muscles  of  animals  after  death,  may  each  cause  a 
contraction  of  the  pupil,  which  may  last  almost  for  an  indefinite 
period;  however,  in  the  state  of  general  relaxation  of  the  muscular 
system  which  follows  prolonged  inhalation  of  chloroform,  a  dilata- 
tion of  the  pupil  may  be  observed.  Examination  of  the  iris  in 
young  mammifcrous  animals  (cat  and  rabbit),  a  few  days  after 
birth,  before  the  eyelids  are  open,  or  before  the  organ  of  sight  has 
been  excited  by  light,  will  show  that  the  pupil  is  widely  dilated, 
and  that  the  iris  exists  in  the  form  of  a  narrow  fillet:  this  appear- 
ance is  not  owing  to  any  want  of  development,  for  the  induced 
current  of  electricity  will  immediately  produce  as  decided  a  con- 
ractiun  of  the  pupil  as  may  be  found  in  the  adult. 


i 


440  ORGANS  OF  THE  SENSES. 

oculorum  (derivations  from  the  lenticular  ganglion  and  nasal 
branch  of  the  ophthalmic  division  of  the  fifth  nerve,  ciliary 
nerves  to  the  number  of  fifteen),  and  the  dilatator  or  radiat- 
ing fibres  by  the  gi'eat  sympathetic  nerve.  The  pupil  dilates 
when  the  light  is  not  strong,  or  when  the  object  presented  is 
at  a  distance,  and  contracts  when  the  contrary  is  the  case. 
These  movements  are  slow^  the  fibres  being  smooth  muscular 
fibres,  like  those  of  the  ciliary  muscle ;  the  movements  of  the 
iris,  like  those  of  this  muscle,  have  a  reflex  character,  and 
belong,  no  doubt,  to  the  same  centre  of  reflexion  (see  p.  59). 
The  iris  appears,  however,  to  be  directly  sensitive  to  the 
action  of  light.  The  will  has  no  power  to  produce  any  move- 
ment of  the  iris,  but  this  may  be  done  indirectly  by  looking 
into  space,  as  if  at  an  object  placed  at  an  infinite  distance, 
and  the  pupil  will  then  dilate ;  this  simple  method  has  been 
frequently  employed,  especially  in  past  times,  for  the  purpose 
of  giving  an  expression  of  ecstasy  to  the  eyes,  this  feeling 
invariably  being  accompanied  with  great  dilatation  of  the 
pupil.  Some  valuable  medicinal  agents  also  possess  the  pro- 
perty of  producing  dilatation  or  contraction :  the  Calabar  bean 
serves  to  contract,  and  belladonna  (atropine)  to  dilate  the 
pupil  for  a  longer  or  shorter  space  of  time. 

The  pupil  is  also  dilated  in  certain  diseases  of  the  brain 
and  cord.  Its  normal  movements  are  more  active  and  fre- 
quent in  some  persons  than  in  others.  We  have  already  seen 
that  these  contractions  have  only  a  subordinate  position  in 
the  process  of  accommodation,  and  we  may,  therefore,  close 
this  part  of  our  subject  by  saying  that  the  iris  is  simply  a 
diaphragm  which  hy  a  reflex  action  decides  the  diameter  of 
its  own  aperture. 

III.  Sensitive  rriemhrane  or  retina. 

The  retina  is  an  extremely  compHcated  membrane  which 
closely  covers  most  of  the  inner  aspect  of  the  choroid  tunic. 
It  is  formed  principally  by  the  bifurcations  or  subdivisions  of 
filaments  of  the  optic  nerve,  to  the  extremity  of  which  special 
tenninal  organs  are  attached.  The  optic  nerve  passes  through 
all  the  tunics  or  envelopes  of  the  eye,  at  a  point  situated  a 
little  within  the  posterior  extremity  of  the  antero-posterior 
axis  of  the  globe  of  the  eye,  and,  as  it  reaches  the  inner  aspect 
jof  the  choroid  tunic  (Fig.  119,  P.),  it  expands  {optic papilla 
or  optic  disk),  and  thus  forms  the  internal  layer  oi  the  retina; 
subsequently  the  fibres  of  this  layer  bend  and  turn  outwards 
(Fig.  120),  forming  thiis,  by  their  juxtaposition,  the  substance 


SENSE  OF  SIGHT. 


441 


of  the  membrane  of  the  retina.  In  the  course  of  their  short 
passage,  these  fibres  exhibit  swellings,  the  signification  of 
which  is  unknown.  Some  of  these  form  genuine  nerve  cells, 
and  terminate  by  dilating  into  a  peculiar  element,  which  is 
either  small  and  delicate  (rods,  or  larger  and  more  bulky 


Fig.  119.  — Diagram  of  the  retina  and  the  optic  nerve.* 


(cones)  Fig.  120)  ;  we  see,  by  this  arrangement,  that  the  rods 
and  cones  form,  by  their  juxtaposition,  the  external  layer  of 
the  retina  (Fig.  119) ;  this  layer,  which  is  easily  separated, 
was  long  known  under  the  name  of  Jacob's  membrane. 

Max  Schultze  and  other  German  histologists  who  have 
lately  made  investigations  on  this  subject  fix  the  number  of 
layers  at  ten,  which,  thus  stratified,  form  the  substance  of  the 
retina.  These  are,  beginning  from  within  (proceeding  from 
the  vitreous  humor  to  the  choroid  tunic)  an  internal  limiting 
membrane  (Fig.  120,  /)  ;  the  layer  of  filaments  of  the  optic 
nerve  (Fig.  120,  /)  ;  the  layer  of  the  nerve  cells  (g) ;  the 
granular  layer  (7i) ;  the  internal  nuclear  division  of  the  gran- 
ular layer  (k) ;  the  external  nuclear  division  of  the  granular 
layer ;  external  granular  layer  (k')  ;  external  limiting  mem- 
brane of  Schultze;  the  layer  of  cones  and  rods  (Fig.  120,  s); 
and,  finally,  a  layer  of  pigment,  which  is  diffused  between 
the  extremities  of  the  cones  and  rods,  and  which  every  thing 

*  S,  S,  Sclerotic.  C^,  Choroid.  Nop,  Optic  nerve.  P,  Its  papilla,  whence 
the  fibres  radiate,  and  form  the  retina  (K,  R).  M,  Central  fosselte  of  me  .retina 
{oTjbvea  centralis  rttinoi). 


442 


ORGANS  OF  THE  SENSES. 


tends  to  prove  rather  a  part  of  the  retina  than  of  the  choroid 
tunic. 

The  retina  is  much  thinner  in  one  part  than  in  others ;  in 
dther  words,  the  passage  of  the  nerve  filaments  from  within  to 
without  is  much  shorter;  they  exhibit  no  enlargement,  and 
end  directly  in  their  terminal  organ.     This  point,  which  is 


Fig.  120.  —Elements  and  structure  of  the  retina.* 

tinged  yellow,  is  known  by  the  name  of  yellow  spot  {macula 
luted).,  and  is  (Fig.  121)  situated  a  httle  outside  of  the  optic 
papilla,  or  precisely  at  the  posterior  extremity  of  the  antero- 
posterior diameter  of  the  globe  of  the  eye.  At  this  pointy 
the  terminal  organs  are  all  represented  by  cones^  while  in 
other  parts  the  rods  and  cones  are  intermixed,  the  former 
becoming  more  rare  as  we  examine  the  anterior  part  of  the 
retina,  that  is,  the  part  farthest  from  the  yellow  spot.  At 
this  part  of  the  retina  (region  of  the  ora  serrata ;  see  p. 
437,  Fig.  118,  15),  all  elements  of  which  partake  of  the 
nature  of  nerves  gradually  disappear,  their  place  being 
occupied  by  connective  tissue  elements,  which  are  also  found, 

*  A,  Vertical  section  of  the  substance  of  the  retina,  hardened  by  chromic 
acid.  /,  Membrane,  called  the  membrana  limitans,  with  the  ascending  support- 
ing fibres  (of  MuUer).  /,  Layer  of  filaments  of  the  optic  nerve,  q^  Layer  of 
the  nerve  cells.  «,  Gray  layer,  finally  gi-anular,  crossed  by  radiatmg  fibres. 
k,  Interior  (anterior)  granular  layer.  ^,  Intergranular  layer.  A;',  Exterior  (pos- 
terior) granular  layer,  s.  Layer  of  the  rods  and  cones.  B  and  C,  Detached 
lilameut*,  enlarged. 


SENSE  OF  SIGHT. 


443 


though  in  very  small  quantities,  in  the  other  parts  of  the 
retina. 

Finally,  the  retina  contains  vessels,  and  terminal  branches 
of  the  central  artery  of  the  optic  nerve,  which  emerges  in 
the  centre  of  the  papilla,  and  surrounds  the  yellow  spot 
with  its  ramifications  (Fig.  121). 


■Appearance  ot  tne  posterior  half  of  the  retina  of  the  left  eye, 
examined  with  the  ophthalmoscope  (Liebreich). 

The  retina  forms  essentially  the  sensitive  membrane  of  the 
^y®  >  by  whatever  cause  its  sensibility  is  excited,  it  always 
gives  rise,  as  a  subjective  phenomenon,  to  what  is  known  by 
the  name  of  luminous  sensation.  If  the  retina  be  pricked 
(Magendie),  compressed  {phosphenes^phosphaince^  studied  by 
Serre  of  Uzes),  twitched  by  any  sudden  movement  of  the 
eye,  or,  in  short,  excited  in  any  way,  an  impression  of  light 
will  be  produced  ;  the  same  effect  follows  the  use  of  electric- 
ity. The  special  method,  by  means  of  which  the  luminous 
sensation  is  distinguislied  from  all  others,  does  not,  therefore, 
reside  in  the  qualities  which  are  peculiar  to  external  light ; 
there  is  no  exclusive  connection  between  light  and  luminous 


444  ORGANS  OF  THE  SENSES. 

sensation.  Light  is  only  the  usual  normal  and  physiological 
excitant  of  this  sensation ;  the  retina,  being  situated  in  the 
depth  of  the  eyeball,  and  protected  by  the  cavity  of  the 
orbit,  is  almost  entirely  removed  from  the  influence  of  all 
other  agents  than  the  rays  of  light;  these  are  able  to  reach  it 
unobstructed  by  passing  through  the  transparent  media  of 
the  eye.  We  have  already  seen  that  in  cases  where  the 
refringent  apparatus  of  the  media  of  the  eye  is  in  woiking 
order,  the  images  of  external  objects  are  painted  (upside- 
down)  upon  the'  retina;  an  impression  is  then  made  upon  the 
membrane,  and  the  excitation  transmitted  to  the  cerebral 
centres  (corpora  quadrigemina  and  cerebral  lobes),  by 
means  of  a  peculiar  mechanism,  which  we  shall  endeavor  to 
describe. 

The  retina  is  not,  however,  in  every  part  equally  sensitive 
to  light ;  there  is  a  point  which  is  quite  insensitive  to  it,  viz., 
where  the  optic  nerve  (papilla)  begins,  and  is  called,  on  that 
account,  the  punctitm  ccecum.  This  may  be  easily  proved  by 
the  following  experiment :  if  two  small  objects,  one  of  which 
is  white  and  the  other  red,  be  placed  on  the  same  plane,  at  a 
certain  distance  from  each  other,  and  we  look  at  either  of 
them  with  one  eye  only,  we  shall  see  the  other  also ;  but  if 
the  latter  be  moved  so  as  to  make  its  image  pass  over  the 
whole  retina,  a  moment  will  come  when  this  image  will  be 
formed  exactly  on  the  optic  papilla;  at  that  moment  the 
object  will  be  quite  invisible,  being  depicted  on  the  punctum 
ccecum.  An  experiment  made  by  Mariotte  consists  in  mark- 
ing two  black  points  upon  the  paper,  at  a  distance  of  five 
centimetres  from  each  other,  and  standing  at  a  distance  of 
fifteen  centimetres  from  the  paper,  the  left  eye  being  closed, 
while  the  point  on  the  left  side  (A)  is  observed  with  the 
right  eye ;  in  this  position  the  point  on  the  right  side  (B) 
will  not  be  seen,  but  it  will  become  visible  in  any  other  part, 
whether  nearer  or  farther  off.    We  find,  by  calculation,  that, 


in  the  position  indicated,  the  image  of  the  point  on  the  right 
side  falls  upon  the  punctum  caecum^  and,  consequently,  is 
invisible. 

The  sensibility  of  the  retina  in  other  parts  differs  greatly ; 
it  reaches  its  highest  point  in  the  yellow  spot  (which  corre- 
sponds exactly  with  the  posterior  pole  of  the  eye)  and  de- 


SENSE  OF  SIGHT.  445 

creases  in  the  anterior  part ;  thus  it  is  150  times  less  at  the 
equatorial  plane  of  the  eye  than  in  the  yellow  spot  or 
macula  lutea  ;  thus,  if  we  place  two  wires  very  close  together, 
but  with  sufficient  space  between  them  to  enable  us  to  dis- 
tinguish one  from  the  other,  and  then  so  direct  the  eye  that 
their  image  shall  fall,  first  upon  the  yellow  spot,  and  then  upon 
the  great  circle  of  the  eye,  we  shall  find,  in  the  latter  case, 
that  the  wires  to  seem  distinct  must  be  placed  at  a  distance 
from  each  other  150  times  greater  than  when  they  are  painted 
upon  the  yellow  spot.  This  experiment  is  exactly  similar  to 
that  made  in  regard  to  the  distance  between  the  points  of 
the  dividers,  by  means  of  which  we  estimated  the  degree  of 
sensibility  of  the  skin  (see  p.  398). 

The  yellow  spot  is,  therefore,  the  principal  seat  of  distinct 
vision.  We  make  use  chiefly  of  this  in  order  to  see  clearly, 
and  all  the  movements  of  the  eyeball  are  designed  to  bring 
the  image  of  the  objects  observed  to  this  extremely  sensitive 
point  in  the  eye.  The  entire  surfiice  of  the  retina  is  about 
15  square  centimetres,  while  the  surface  of  the  macula  lutea 
is  only  1  millimetre  ;  we  therefore  make  use  of  only  -^^^  part 
of  the  surface  of  the  retina  for  the  purpose  of  distinct  vision. 
Thus,  in  reading,  we  see  distinctly  only  two  or  three  words 
at  a  time,  their  image  would  fall  directly  on  the  yellow  spot ; 
and  the  eye  must  pass  over  the  whole  line  in  order  to  read 
it ;  in  other  words,  it  must  bring  the  image  of  every  single 
word  to  the  sensitive  point.  In  order  to  decide  exactly  what 
is  the  number  of  letters,  or  the  extent  of  surface,  painted 
on  the  retina,  the  eyes  are  fixed,  in  a  dark  room,  upon  the 
page  of  a  book ;  the  number  of  letters  which  can  be  seen  by  a 
flash  of  lightning  or  by  an  electric  spark,  is  then  counted,  and 
the  dimensions  calculated.  Starting  from  this  datum,  the 
known  dimensions  of  the  yellow  spot  may  be  calculated. 

Having  observed  the  various  degrees  of  sensibility  of  the 
different  parts  of  the  retina,  we  must  now  examine  the  sub- 
stance of  this  membrane,  and  see  whether,  among  its  numer- 
ous layers,  there  is  not  one  which  is  peculiarly  sensitive,  and 
containing  an  element  which  is  essentially  susceptible  to  the 
influence  of  light.  A  simple  experiment  will  supply  us  with 
a  sufficiently  satisfactory  answer  to  this  inquiry :  this  experi- 
ment is  known  by  the  name  of  Purkinje's  vascular  tree^  and 
consists  in  the  perception  of  the  vessels,  or,  rather,  of  the 
shadow  of  the  vessels  of  the  retina  itself.  These  vessels, 
which  are  situated  in  the  anterior  layers  of  the  retina,  always 
cast  their  shado^^'  upon  the  posterior  layers  of  this  membrare, 


446  ORGANS  OF  THE  SENSES. 

and  we  can  only  suppose  that  it  is  the  force  of  habit  which 
prevents  our  being  generally  conscious  of  this  shadow ;  the 
question  was,  whether  it  could  not  be  rendered  visible  by 
being  thrown,  artificially,  upon  some  other  part  of  the  eye. 
This  was  done  in  the  following  manner:^  the  person  making 
the  experiment  looks  r.t  a  dark  obscurity,  while  a  lighted 
candle  is  placed  either  below,  or  at  the  side  of  his  eye  (Fig. 
122);  the  rays  proceeding  from  this  light  (B)  will  be  con- 
centrated by  the  crystalline  lens  u])on  a  point  very  much  to 
one  side  of  the  retina,  the  source  of  light  (the  candle)  being 
very  far  beyond  the  visual  centre.  The  image  of  the  candle 
on  the  retina  itself  constitutes  an  interior  source  of  light  (B') 
which  is  sufficiently  strong  to  carry  a  considerable  quantity  of 
light  into  the  vitreous  body.  It  is  plain  that,  under  the  in- 
fluence of  this  light,  the  vessels  of  the  retina  (C  and  D)  will 
cast  their  shadow  upon  the  posteiior 
layers  of  the  retina,  not,  however,  in  the 
usual  portions  (that  is,  C  and  D').  The 
shadow  will  be  disj)laced,  and  thrown 
upon  the  side  opposite  to  that  of  the 
source  of  light  in  the  retina,  which  is  on 
the  same  side  as  the  c;indle  (the  original 
source  of  light).  The  field  of  vision 
being  then  illuminated  by  a  light  of  a 
^*^- 122. —Experiment  yellowish  red,  a  network  of  dark-colored 
vessels  is  seen  to  appear,  exactly  resem- 
bling thevesselsof  the  retina,  as  sketched  from  an  anatomical 
preparation.     (  Vascular  tree  of  Purkinje.) 

The  posterior  layers  of  the  retina  are,  therefore,  sensitive 
to  light ;  but  this  experiment  shows  us  which  of  these  layers 
is  especially  sensitive.  By  means  of  a  mathematical  process 
which  we  cannot  noAV  describe,  and  judging  by  the  move- 
ments of  the  shadows  of  the  vessels  when  the  source  of  light 
is  displaced,  or,  in  other  words,  by  the  apparent  magnitude 
of  the  movement  produced  in  the  field  of  vision  by  the  vas- 
cular tree,  Helmholtz  has  infeiTcd  that  the  layer  which  receives 

^  See  HelmhoJtz,  "  Optique  Physiologique."  Traduct.  frang. 
par  E.  Javal  et  Th.  lOein.     Paris,  18G7,  p.  211. 

*  B,  A  candle  placed  at  the  side  of  the  eye,  that  is,  as  much  to  the  side  of 
the  centre  of  the  cornea  as  possible.  B',  Jnterior  luminous  source,  formed  by 
the  rays  of  light  concentrated  by  the  crystalline  lens  upon  the  extreme  lateral 
portion  of  the  eye.  CD,  Two  vessels  of  the  retina  (the  size  of  the  retina  is  hero 
greatly  cxaijgerated).  The  shadow  of  these  two  vessels  is  seen  as  if  projected 
at  D'  and  &. 


SENSE   OF  SIGHT.  447 

these  shadows,  is  separated  from  these  vessels  by  a  distance 
which  is  exactly  equal  to  that  which  by  microscopical  men- 
surations of  sections  of  the  retina  exists  between  the  layer  in 
which  the  vessels  are  situated  and  Jacob's  membrane ;  the 
sensitive  layer  of  the  retina  consists^  therefore^  of  the  layer 
of  rods  and  cones. 

Now  that  we  have  seen  that  the  seat  of  sensibility  is  in 
one  of  the  layers  of  the  retina,  the  extreme  posterior  layer, 
we  can  no  longer  be  content  with  the  empty  formula  that  the 
retina  is  a  screen;  nor  consider  it  sufficient  to  trace  the  prog- 
ress of  the  light  through  the  media  of  the  eye  to  the  surface 
of  the  sphere  of  the  retina.  The  rays  of  light  pass  through 
all  the  layers  of  the  retina  without  making  any  impression, 
as  has  been  shown,  first  by  Rouget,  and  since  by  Desmoulins ; 
on  reaching  the  part  where  they  come  in  contact  with  the 
rods  and  the  choroid  tunic,  they  are  reflected ;  and,  as  the 
optical  centre  obviously  coincides  with  the  centre  of  the  ret- 
inal curve,  the  reflexion  naturally  takes  place  in  the  direction 
of  the  axis  of  the  rods  and  cones.  The  external  segments  of 
the  cones  and  the  rods,  however,  as  has  been  proved  by 
Schultze,^  consist  of  small  lamellae,  placed  one  upon  the  other ; 
and  these,  on  account  of  their  structure  and  optical  proper- 
ties, cannot  be  considered  as  being  susceptible  to  light,  but 
only  as  organs  which  serve  to  modify  the  light.  It  is  now 
generally  supposed  that  at  the  instant  when  the  Hght  reflected 
by  the  choroid  mirror  (Rouget)  passes  back  through  the 
retina,  a  peculiar  transformation  takes  place  in  these  organs, 
constituting  a  sort  of  necessary  intermediation  between  the 
physical  phenomenon  of  light,  and  the  physiological  phenom- 
enon of  nervous  excitation.  Without  exactly  defining  the  in- 
timate nature  of  the  process  which  here  occurs,  we  may  con- 
sider it  as  a  transformation  of  force  ;  in  other  words,  the 
luminous  movement  (vibrations  of  the  ether)  is  changed  into  a 
nervous  movement  (nervous  vibration.  See  p.  29).  The  ex- 
ternal parts  of  the  rods  and  cones  are,  in  themselves,  insensi- 
tive to  luminous  impressions,  but  they  form  organs  of  trans- 
formation of  the  waves  of  light,  that  is,  special  agents  by 
which  the  light  is  transmitted  to  the  optic  nerve. 

The  internal  segments  of  the  rods  and  cones  are  then  the 
organs  which  are  essentially  susceptible  to  light.  The  dif- 
ferences of  function,  which  correspond  with  the  differences 

^  See  a  resume  of  these  researches.  Duval,  "  Structure  et 
Usage  de  la  Ketine."     Paris,  1873.     These  d'Agreg.  ' 


448  ORGANS  OF  THE  SENSES. 

of  form  and  structure  observed  between  the  rods  and 
cones,  from  Schultze's  researches,  appear  to  consist  in  this : 
that  the  rods  are  affected  only  by  differences  in  the  in^ 
tensity  of  the  Hght,  while  the  cones  are  affected  by  differences 
in  its  quality,  that  is,  by  its  color.  Thus  comparative  histol- 
ogy shows  that  the  nocturnal  animals  (the  bat,  the  hedgehog, 
and  mole),  have  no  cones.  We  know  that  it  is  impossible  to 
distinguish  colors  in  the  dark.  The  night-birds  also,  have  no 
cones,  but  simply  rods :  these  are  sufficient  to  enable  them 
to  distinguish  the  differences,  not  in  quality,  but  in  quantity, 
of  the  light.  On  the  other  hand,  the  day-birds,  especially 
those  which  live  on  small  insects  of  brilliant  colors,  possess  a 
proportionate  and  much  larger  number  of  cones  than  man 
or  the  other  mammalia. 

The  impressions  produced  upon  the  retina  exhibit  certain 
interesting  peculiarities ;  one  of  these  being  that  these  im- 
pressions last  for  a  certain  time  after  the  luminous  object  has 
ceased  to  act,  and  if  short  luminous  impressions  succeed  each 
other  rapidly,  they  are  at  length  confused  in  one  continuous 
impression.  Every  one  knows  that  a  live  coal  passed  rapidly 
before  the  eyes  produces  the  effect  of  a  ribbon  or  circle  of 
fire;  because  the  impression  produced,  as  it  passes  before  one 
point  in  the  retina,  lasts  until  the  end  of  the  next  revolution ; 
and  these  successive  impressions  are  so  joined  together  as  to 
show  us,  by  a  line  of  fire,  the  path  of  the  luminous  point. 

On  the  other  hand,  a  very  bright  object,  placed  against  a 
dark  background,  always  seems  to  us  larger  than  it  really  is ; 
while  a  black  or  dark  object,  placed  against  a  luminous  back- 
ground, appears  smaller.  In  order  to  explain  this  phenom- 
enon it  is  supposed  that  the  most  luminous  parts  excite, 
not  only  those  parts  of  the  retina  upon  which  they  are  de- 
picted, but  also  the  adjacent  parts,  and  thus  encroach  upon 
the  images  of  parts  less  strongly  illuminated :  this  phenom- 
enon is  known  under  the  name  of  irradiation.  Thus  a  white 
triangle,  placed  against  a  dark  background,  appears  larger 
than  it  really  is ;  while  its  edges  cease  to  be  rectilinear,  and 
appear  as  curved  lines;  in  short,  the  surfaces  of  the  sides  are 
convex ;  a  black  triangle,  against  a  white  background,  appears 
to  us  smaller  than  it  is,  and  the  surfaces  of  the  sides  will  be 
concave.  A  surface  divided  into  lines  of  equal  breadth,  and 
alternately  black  and  white,  will  appear  to  contain  more 
white  than  black,  the  white  lines  seeming  broader  than  the 
others;  this  explains  why  Gothic  buildings,  blackened  by 
time,  and  standing  out  against  a  brilliant  sky,  appear  to  us 


SENSE  OF  SIGHT.  449 

lighter  and  more  slender  in  outline  than  modern  buildings  of 
white  stone.  M.  Le  Roux's^  researches  show  that  the  phe- 
nomenon of  irradiation  is  peculiar  to  the  field  of  indistinct 
vision  ;  it  increases  with  the  distance  from  the  yellow  spot ; 
the  only  radiation  which  occurs  in  this  part  of  the  retina  is 
that  produced  by  the  limits  of  the  acuteness  of  vision.  The 
radiation  in  the  field  of  indistinct  vision  is  explained  by  the 
progressive  interval  found  between  the  sensitive  elements 
(rods  and  cones),  as  we  get  farther  from  the  yellow  spot 
where  the  highest  degree  of  condensation  takes  place.  These 
phenomena  of  irradiation  may,  in  pathological  conditions 
of  the  brain,  as  in  delirium,  increase  to  such  a  degree  as  to 
completely  upset  the  reason. 

Nearly  all  the  numerous  phenomena  known  by  the  name 
of  optical  illusions  may  be  considered  either  as  instances 
of  thQ  persistence  or  else  of  the  irradiation  of  images  upon 
the  retina.  To  these  must  be  added  the  excitations  which 
take  place  in  the  retina  itself  {subjective  images^  entoptic 
percejJtions).  The  principal  of  these  are  due  to  modifications 
in  the  circulation.  We  have  seen  that  the  retina  contains 
vessels  (pp.  443  and  446)  ;  these  vessels  sometimes  become 
congested,  and  produce  compression  of  the  elements  of  the 
retina,  whicli,  when  slight,  excites  the  sensitive  membrane, 
and,  when  strong,  paralyzes  it. 

Thus,  if  we  lower  and  raise  the  head  suddenly,  we  pro- 
duce subjective  visual  sensations,  consisting  of  bright  and  dark 
spots  which  seem  to  be  impressed  on  the  eye.  Many  cases 
of  blindness  are  owing  to  vascular  derangement  of  the 
retina,  which  may  be  easily  discovered  in  the  living  subject 
by  the  use  of  the  ophthalmoscope. 

Looking  with  the  eye  into  the  microscope,  especially 
when  there  is  no  object  in  the  field,  reveals  other  entoptic 
inages  which  are  extremely  curious;  these  are  muscce  voli- 
tantes  or  specks,  which  appear  under  the  form  of  masses  of 
small  and  very  round  globules,  all  of  which  have  nearly  the 
same  size,  and  are  entangled  with  some  sinuous  filaments. 
Ch.  Robin  has  shown  that  these  images  are  produced  by  the 
l)rojection  on  the  retina  of  the  shadow  of  the  globules  and 
the  filaments  (elements  of  mucous  tissue  or  embryo  connec- 
tive tissue),  which  are  suspended  in  the  vitreous  body?- 

One  circumstance  which  has  greatly  perplexed  physiologists 

^  Academie  des  Sciences.     Avi'il,  1873. 

2  Ch.  Robin,  "  Traite  du  Microscope."     1871,  p.  437. 

29 


450  ORGANS  OF  THE  SENSES. 

consists  in  the  fact  that  we  always  see  objects  upright,  and  in 
their  natural  position,  although  their  image  appears  upside- 
down  on  the  retina;  this  may  be,  however,  readily  explained. 
We  see  objects  erect  and  not  upside-down  because  our  mind 
carries  outwards  every  impression  made  upon  the  retina,  and 
conveys  it  in  the  same  direction  that  the  rays  of  light  must 
necessarily  follow,  according  to  the  laws  of  optics,  in  order  to 
produce  an  impression  on  any  part  of  the  sensitive  mem- 
brane ;  in  other  words,  every  part  of  the  field  of  the  retina 
has  a  part  of  the  external  visual  field  corresponding  to  it,  and 
these  two  are  so  closely  connected,  that  what  takes  place  in 
one  produces  the  corresponding  effect  in  the  other.  Thus, 
when  we  look  at  an  object  so  long  that  the  retina  becomes 
fatigued,  and  the  image  remains  upon  it,  even  when  the  eyes 
are  closed,  the  image  still  appears  upright,  and  not  upside 
down.  It  is  impossible  to  decide  whether  this  is  only  the 
effect  of  habit  and  of  the  education  of  the  senses,  for  cases 
have  been  known  in  which  persons  blind  from  their  birth 
have  seen  objects  upright  and  not  upside-down,  from  the 
very  moment  that  they  were  able  to  see.^ 

1  We  have  already  protested  (see  p.  417)  against  the  ancient 
theory  that  the  retina  simply  resembles  a  screen.  We  have  seen 
that  it  is  not  enough  to  trace  the  passage  of  a  ray  of  light  until  it 
reaches  the  retina,  but  that  we  must  examine  this  after  it  has 
entered  the  sensitive  membrane.  This  examination,  made  as 
above  (p.  447),  gives  us  exactly  what  we  need  for  the  purpose  of 
explaining  why  we  see  objects  upright,  although  their  image  on  the 
retina  is  upside-down.  We  know  that  mechanical  pressure  of  one 
part  of  the  retina  gives  rise  to  a  luminous  image  (phosphaina, 
p.  443),  which  appears  to  be  situated  on  the  side  of  the  field  of 
vision  opposite  to  that  on  which  the  compression  is  made  (see 
Serre  d'Uz^s,  "  Essai  sur  les  Phosphenes  ou  Anneaux  lumineux 
de  la  Retine."  Paris,  1853.)  "  The  position  of  the  subjective 
image  of  the  phosphainae,"  says  Kouget,  "which  image  is  dia- 
metrically opposed  to  the  region  of  the  retina  excited  (although 
this  image  is  entirely  independent  of  the  optical  phenomena  of 
vision),  proves  that  the  impressions  communicated  to  the  extremi- 
ties of  the  nerves  of  the  retina  by  the  intermediation  of  the  rods 
(see  p.  447)  are  carried  beyond  the  eye  in  the  direction  of  the  prolonged 
axes  of  the  rods.  The  prolonged  axes  cross  each  other  at  the 
centre  of  the  curve  of  the  retina  (in  the  eye),  the  rods  being 
arranged  according  to  the  rays  of  this  curve.  After  tlieir  intersec- 
tion, they  are  outside  of  the  eye,  in  the  part  in  vvhicl  the  subjec- 
tive image  is  produced,  the  direction  being  the  reverse  of  that  of 
the  rods  themselves,  the  prolonged  axes  of  the  rods  of  the  upper 
region  of  the  retina  corresj)onding  to  the  lower  part  of  the  sub- 


SENSE  OF  SIGHT.  451 

We  must  also  inquire  how  it  happens  that,  having  two  eyes^ 
we  do  not  see  double.  In  order  to  produce  a  single  impres- 
fiion  upon  the  central  nervous  organs  of  the  brain,  any  object 
whose  image  falls  upon  both  eyes,  and,  consequently,  forms 
two  impressions  on  the  retina,  must  be  depicted  upon  two 
similar  points  in  each  retina.  Seeing  double,  as  in  strabis- 
mus, is  caused  by  a  want  of  symmetry  between  the  part  dis- 
turbed in  each  retina  (see  p.  36).  We  must,  however,  add 
that  the  necessity  for  the  impression  being  made  upon  two 
exactly  similar  points  in  the  two  retinae,  is  only  the  effect  of 
habit,  and  is  by  no  means  pre-established,  or  necessarily  con- 
nected with  the  anatomical  arrangement  of  the  eye,  as  im- 
plied in  J.  MuUer's  nativistic  theory.  Tliis  theory  has  lately 
yielded  to  the  empirical  theory,  owing  to  Helmholtz's  success- 
ful experiments.  Preparations  made  during  observation  with 
a  compound  microscope,  in  which  images  are  reversed,  will 
enable  us  to  direct  the  movements  of  the  eye  without  express 
attention  or  care,  though  these  are  associated  with  a  percej)- 
tion  exactly  opposed  to  our  natural  habit  of  vision.  Persons 
who  are  cross-eyed  or  who  squint  (afflicted  with  strabismus) 
are  not  accustomed  to  blend  in  one  the  two  images  which 
impinge  upon  non-coincident  points  in  the  two  retinae,  and 
this  habit  becomes  so  strong,  that  immediately  after  the  eye 
has  been  restored  to  its  natural  position,  there  is  diplopia  or 
double  vision,  though  the  image  of  any  object  be  brought 
to  bear  upon  corresponding  or  coincident  points  on  the  retinae ; 
the  good  effects  of  the  operation  for  strabismus  are  slowly 
developed.-^ 

jcctive  image  (phosphainse,  and  those  of  the  lower  to  the  upper 
part,  etc.).  This  inversion  also  takes  place  when,  instead  of  a 
solid  body  (the  extremity  of  the  finger  for  the  phosphainaB) ,  the 
reversed  image  is  formed  upon  the  choroid  mirror  (p.  447),  which, 
after  reflexion,  causes  the  rods  to  vibrate  in  the  direction  of  their 
axis.  In  this  manner,  the  physical  (optical)  reversion,  produced  by 
the  intersection  of  the  luminous  rays  at  the  nodal  point,  is  formed 
and  cancelled.  In  short,  the  image,  reversed  by  the  optical  conditions 
of  the  eye,  is  restored  by  the  physiological  mechanism  of  the  sensations 
when  carried  to  a  distance  from  the  point  excited,  in  the  same  way  as 
the  sensation  of  tingling  of  the  skin  (see  p.  53,  Eccentricity  of  the 
sensations),  caused  by  a  medullary  congestion,  extends  far  beyond 
the  part  excited.  A  better  illustration  of  this  is  seen  in  persons 
who  have  lost  a  limb,  and  feel  the  sensation  in  the  stump,  spread, 
as  it  were,  to  the  extremity  of  the  fingers." 

1  See  E.  Javal,  Art.  "  Diplopie,"  in  the  "  Nouv.  Diet,  de  Med. 
et  de  Chirur.  Prat."     Vol.  XI.  p.  653. 


452  ORGANS  OF  THE  SENSES. 

The  visual  appreciation  for  perspective  is  a  mental  percep- 
tion. The  stereoscope  produces  a  complete  illusion  of  this 
kind,  doing  for  the  mind  what  the  latter  would  otherwise  be 
obliged  to  do  for  itself.  In  short,  according  to  Ilelmholtz,  in 
the  use  of  the  stereoscope,  we  are  conscious  of  two  simulta- 
neous sensations  which  are  quite  distinct  from  each  other ;  the 
blending  of  these  two  into  a  single  image  of  the  external 
object  is  not  caused  by  any  pre-established  mechanism  for 
the  excitation  of  the  organ  of  sense,  but  by  the  exercise  of 
the  intellectual  faculty. 

A  satisfactory  answer  to  questions  of  this  kind  is  to  be 
found  in  the  case  of  persons  who  are  born  blind,  and 
have  been  successfully  operated  upon.  When  they  first 
receive  their  sight,  their  visual  impressioiis  are  the  same  as 
ours,  but  the  centre  of  visual  perceptions  has  not  received  the 
same  education,  in  regard  to  its  relation  with  other  centres; 
they  lack  what  we  have  acquired.  They  usually  imagine, 
when  they  behold  the  outer  world  for  the  first  time,  that 
every  thing  wliich  they  perceive  touches  their  eyes ;  they  have 
neither  the  power  of  localizing  nor  of  interpreting  the  im- 
pressions made  upon  the  retina.^ 

IV.  Appendages  of  the  eye. 

The  appendages  of  the  eye  consist  of  the  muscles  by  which 
the  eyeball  is  moved,  and  the  lachrymal  system  which  pro- 
tects tiie  front  or  exposed  surface  of  this  globe. 

Muscles  of  the  Eye.  —  Jf  we  consider  how  small  a  part  of 
the  retina  is  really  sensitive,  we  shall  underatand  the  impor- 
tance of  the  movements  of  the  globe  of  the  eye  or  eyeball. 
The  eye  may,  indeed,  be  considered  as  a  somewhat  narrow 
tube,  which  we  can  turn  in  any  direction,  for  the  purpose  of 
bringing  the  image  of  external  objects  into  its  deep  median 
part.  These  movements  are  effected  by  the  muscles  of  the 
globe  of  the  eye.  These  muscles  are,  first,  the  recti  muscles^ 
whose  action  we  can  readily  understand.  These  are  either 
elevator  or  depressor  muscles  (superior  and  inferior  recti 
muscles),  abductor  or  adductor  muscles  (the  external  and 
internal  recti  muscles).  The  internal  recti  muscles  are  espe- 
cially important  because  they  serve  to  make  the  two  visual 
axes  converge  towards  an  object  looked  at  with  both  eyes. 
The  combination  of  these  muscles  gives  rise  to  every  possible 

1  See  the  well-known  history  ©f  the  blind  man  of  Cheselden, 
in  H.  Taine,  *'  De  I'lntelligence,"  Vol.-  II.  Ch.  2. 


SENSE  OF  SIGHT.    ,  453 

movement.  Another  group  of  two  muscles  exists,  whose 
office  it  is  to  produce  in  the  globe  a  movement  of  rotation , 
upon  its  antero-posterior  axis.  These  are  the  two  oblique 
muscles.  By  careful  examination  of  the  points  of  insertion 
or  reflection  of  these  muscles  (the  pulley  (trochlea)  of  the 
trochlearis^  or  superior  oblique  muscle)  we  find  that  they 
both  serve  to  direct  the  pupil  outwards,  and  also  to  produce 
in  it  a  rotary  movement,  the  direction  of  which,  in  the  right 
eye,  for  instance,  under  the  influence  of  the  superior  oblique 
muscle,  will  be  the  same  as  that  of  the  hands  of  a  watch, 
and  the  reverse,  when  under  the  influence  of  the  small 
oblique  muscle.  The  purpose  of  these  rotary  movements 
appears  to  be  to  counterbalance  those  of  the  head,  and  to 
maintain  the  parallelism  of  the  two  eyes,  when  the  head  is 
bent  on  one  side  or  the  other. 

The  oblique  muscles  also  extend  from  the  front  to  the  back, 
being  inserted  in  the  posterior  hemisphere  of  the  globe  of  the 
eye ;  they  thus  draw  the  globe  forwards,  and  wlien  this 
movement  coincides  with  that  of  the  recti  muscles,  which 
draw  the  globe  slightly  backwards,  and,  especially,  with  that 
of  the  orbicularis  palpebrarum,  which  compresses  it  from 
front  to  back,  a  sort  of  compression  of  the  globe  of  the  eye  is 
the  result:  this  compression  is  intended  to  prevent  too 
violent  congestion  of  the  eye,  which  is  thus  compressed  as  a 
person  would  compress  a  sponge.  In  the  same  way,  when 
making  violent  efforts  which  send  the  blood  to  the  head,  we 
instinctively  close  our  eyes,  and  forcibly  contract  the  muscles 
attached  to  them;  children  who  scream  so  violently  that 
their  face  becomes  suffused  with  blood,  shut  their  eyes  tight 
while  doing  so,  and,  no  doubt,  at  the  same  time  contract  the 
oblique  muscles.^ 

'  See,  on  this  subject,  some  extremely  original  ideas  of  Dar- 
win's on  the  movements  of  the  face  in  regard  to  the  expression  of 
painful  and  sad  emotions.  "  When  children  scream  loudly,  the 
action  of  screaming  produces  a  great  change  in  the  circulation,  the 
blood  being  carried  to  the  head,  and  especially  to  the  eyes,  pro- 
ducing a  disagreeable  sensation.  Charles  Hell  has  observed  that, 
under  these  circumstances,  the  muscles  which  surround  the  eyes 
contract  in  such  a  manner  as  to  protect  them.  This  action  has 
become,  by  the  ellect  of  natural  selection  and  inheritance,  an  in- 
stinctive habit.  As  man  advances  to  mature  age,  he  learns  to  con- 
trol, in  a  great  measure,  the  disposition  to  cry  out,  having  found 
indulgence  in  it  painful;  he  is  thus  able  to  avoid  the  contraction  of 
the  corrugator  muscles,  but  can  prevent  that  of  the  pyramidal 


454  ORGANS  OF  THE  SENSES. 

The  study  of  the  muscles  of  the  eye  is  connected  with 
that  of  the  muscles  of  the  eyelids ;  of  these  there  are  two 
muscles :  the  elevator  of  the  upper  eyelid  {levator  palpebrm 
superioris)  and  the  orbicularis  palpebrarum.  The  levator 
palpebra^^  which  is  over  the  superior  rectus  muscle  of  the  eye, 
seems  almost  superfluous,  for  the  last-mentioned  muscle,  by 
the  fibres  which  connect  it  with  the  upper  eyelid,  would  be 
sufiicient  to  raise  the  latter  at  such  times  as  it  directs 
the  pupil  upwards.  The  elevator  muscle  serves,  however,  to 
keep  the  palpebral  aperture  wide  open,  and,  during  our  wak- 
ing moments,  it  reposes  only  for  a  few  seconds  at  a  time,  and 
at  irregular  variable  intervals,  when  the  eyes  are  closed  by 
winking.  The  orbicular  muscle  is,  like  all  other  sphincters, 
formed  of  fibres  in  the  form  of  a  loop  or  a  circle,  but  exhibits 
on  every  side,  and  especially  on  its  nasal  aspect,  genuine 
insertions  in  the  form  of  bony  adhesions,  so  that  in  contracting, 
the  palpebral  opening  is  reduced  to  a  transverse  slit,  instead 
of  to  a  point :  this  is  also  owing  to  the  fact  that  the  eyelids  con- 
tain, in  their  substance,  thick  layers  of  resisting  fibrous  tissue 
(called  tarsal  cartilages).  The  functions  of  this  sphincter 
appear  to  be  supplementary  to  that  of  the  orbicular  muscle 
of  the  iris:  like  the  latter  it  contracts  under  the  influence  of 
sensations  on  the  retina,  as,  for  instance,  when  the  light  is  too 
strong;  but  it  also  contracts  under  the  influence  of  reflex 
irritations  originating  at  the  cornea.  Thus  it  is  extremely 
difiicult  to  keep  the  eye  open  when  any  foreign  body  touches 
the  surface  of  the  cornea,  and  diseases  of  this  surface  fre- 
quently give  rise  to  actual  spasms  of  the  eyelids. 

The  Lachrymal  Apparatus.  —  This  is  composed  of  a  gland 
which  secretes  the  lachrymal  fluid  or  tears,  eyelids^  whose 
oflice  it  is  to  spread  this  fluid  over  the  anterior  surface  of  the 
globe  of  the  eye,  and,  finally,  of  a  series  of  tubes^  by  which 
the  fluid  is  pumped  up,  and  carried  into  the  nasal  chambers. 

The  lachrymal  gland^  which  is  formed  of  lobules  similar 
to  those  of  the  salivary  glands,  is  situated  in  the  upper  part 
of  the  outer  angle  of  the  eye ;  gravitation  is  sufiicient  to  con- 
vey the  secretion  to  the  external  surface  of  the  globe ;  this 

muscles  of  the  nose,  which  are  little  affected  by  the  will,  and  only 
by  the  contraction  of  the  internal  fibres  of  the  frontal  an uscle ;  it  is 
precisely  the  contraction  of  the  centre  of  this  muscle  which  raises 
the  inner  extremities  of  the  eyebrows,  and  imparts  the  character- 
istic expression  of  sadness  to  the  face."  (Leon  Dumont,  *'  Ex- 
pression des  Sentiments,  d'apres  Darwin,"  in  "  Revue  des  Cours 
Scientifiques."     Mai,  1873. 


SENSE  OF  SIGHT.  455 

consists  of  a  limpid,  colorless,  and  alkaline  fluid,  containing  a 
small  quantity  of  albumen  and  salts,  especially  chloride  of 
sodium.  The  tears  are  diffused  over  the  eye,  from  its  outer 
to  its  inner  angle,  by  means  of  the  movements  of  the  orbic- 
ular muscle  alone ;  the  winking  of  the  eyes  spreads  the  tears 
over  the  conjunctiva;  all  the  surfaces,  in  fact,  which  are 
moistened  with  the  tears,  are  covered  by  a  mucous  surface, 
called  the  conjunctiva^  wiiich  extends  from  the  posterior 
surface  of  the  eyelids  to  the  anterior  surface  of  the  globe  of 
the  eye  (upper  and  low^er  portions  of  the  conjunctiva),  and 
lines  the  extreme  anterior  portion  of  the  sclerotic  coat,  as 
also  the  cornea,  as  we  learned  while  studying  that  membrane 
(anterior  epithelial  coat).  The  winking  of  the  eyelids  thus 
secures  the  translucency  of  the  cornea,  by  the  dilfusion  of  a 
liquid  which  constantly  moistens  it,  and  forms,  at  the  same 
time,  such  a  delicate  and  uniform  covering  that  vision  is  not 
obscured.      Winking  may  therefore  be  said  to  be  to  the  eye 


Fig.  124. — Lachrymal  apparatus  * 

what  deglutition  is  to  the  ear  (see  p.  222),  both  movements 
being  intermittent  and  very  frequent.  One  of  the  earliest 
effects  produced  by  paralysis  of  the  eyelids  is  inflammation  of 
the  cornea,  which,  not  being  protected  by  the  diffusion  of  the 
tears,  becomes  liable  to  injury  from  the  air  and  dust. 

*  Lachrymal  apparatus  seen  from  the  conjunctival  surface  of  the  eyelids. 
Meibomian  glands  are  seen  to  run  along  the  edge  of  the  eyelids.  I,  Lachrymal 
gland.  </,  Orifices  of  its  seven  or  eight  excretory  ducts,  at  the  external  angle 
of  the  upper  conjunctival  cul-de-sac;  at  the  inner  exttcmitv  of  the  edges  of  the 
eyelids  are  seen  the  oriliccs'  of  the  lachrymal  points  (in  the  lachrymal  tubercles), 
o,  0,  Orbicular  muscle  (orbital  portion). 


456  ORGANS  OF  THE  SENSES. 

The  secretion  of  the  tears  is  constant ;  it  is  increased  by 
moral  causes,  or  by  reflex  irritations  of  the  cornea,  but  some- 
times also  from  the  nasal  mucous  surface  or  from  the  retina. 
If  the  cornea  be  irritated  by  any  foreign  body,  a  hypersecre- 
tion of  tears  follows  from  the  irritating  nature  of  the  substance 
that  is  dissolved  or  carried  away.  This  secretion  is  produced 
by  a  reflex  phenomenon  exactly  resembling  that  which 
governs  the  secretion  of  the  saliva.  The  centrifugal  nerve 
of  this  reflex  action  is  the  lachrymal  nerve  (a  branch  of  the 
ophthalmic  nerve  coming  from  the  fifth  pair).  The  hyper- 
secretion of  tears  which,  by  a  reflex  action,  follows  the  irrita- 
tion of  many  of  the  cranial  nerves  (the  frontal,  the  nasal,  the 
lingual,  the  glosso-pharyngeal,  and  the  pneumo-gastric  nerves), 
discontinues  after  section  of  the  lachrymal  nerve.  According 
to  Demtschenko,  irritation  of  the  great  sympathetic  nerve 
also  causes  lachrymal  hypersecretion,  in  the  same  way  as  we 
have  seen  that  it  occasions  the  secretion  of  saliva  (see  p.  218) ; 
in  this  case,  however,  the  tears  are  of  a  peculiar  nature,  ro- 
Bembling  the  saliva  under  similar  circumstances  ;  the  secretion 
is  thick  and  cloudy,  while  that  following  irritation  of  the  tri- 
facial, is  limpid  and  transparent^  (compare  with  this  what  is 
said  on  p.  219). 

The  tears  evaporate  to  a  certain  extent,  but  a  portion 
always  remjyns ;  this  portion  is  prevented  from  flowing  over 
the  eyelids  and  running  down  the  cheeks,  by  means  of  the 
iatty  secretion  of  the  meibomian  glands  (see  sebaceous  glands 
and  their  functions)  ;  these  latter  are  found  on  the  edges  of 
the  eyelids,  and  are  more  numerous  in  the  inner  angle  of  the 
eye.  From  here  the  tears  pass  (Fig.  123),  by  the  puncta 
lachrymalia^  successively  through  the  lachrymal  canals^  the 
lachrymal  sack^  and  the  nasal  duct.,  until  they  reach  the 
nasal  chambers,  at  the  anterior  portion  of  the  inferior  meatus. 
Many  reasons,  some  of  more  weight  than  others,  have  been 
suggested,  in  order  to  account  for  the  passage  of  the  lachry- 
mal fluid  through  this  series  of  tubes ;  some  have  supposed 
it  to  be  produced  by  capillarity^  but  this  physical  force,  by 
means  of  which  a  fluid  penetrates  a  small  empty  tube,  is 
rather  a  hinderance  than  an.  aid  to  movement,  if  the  tube  is 
full.^     This  is  likewise  true  of  the  comparison  of  the  lachry- 

^  Demtschenko,  '*  Zur  Innervation  der  Thranendriise."  Pflii- 
ger's  Archiv.,  Sept.,  1872. 

1  See  Foltz,  "  Des  Voies  Lacrymales."  *' Journal  de  Physio- 
logie,"  by  Brown- Sequard.     Vol.  V.,  1862. 


SENSE  OF  SIGHT.  457 

mal  tubes  to  a  siphon.  It  seems  most  probable  that  in  the 
movements  of  inspiration,  the  rarefaction  of  the  air  in  the 
nasal  chambers  occasions  an  aspiration  in  the  nasal  duct,  and 
consequently  by  attraction  through  the  whole  series  of  tubes 
and  sacs ;  in  the  normal  state,  this  slight  aspiration  is  suffi- 
cient to  give  rise  to  the  passage  of  the  tears ;  thus,  when  the 
tears  flow  in  great  abundance,  we  facilitate  their  passage  by 
short  inspirations  or  sobs.  The  lachrymal  tubes  are  furnished 
with  valves,  varying  in  number,  but  all  so  arranged  as  to 
allow  the  tears  to  flow  in  one  direction  only,  and  to  prevent 
any  reflux. 

Not  only  does  the  passage  of  the  air  through  the  nostrils 
enable  us  to  understand  how  the  tears  flow  into  the  nasal 
tube,  but  it  appears  that,  on  the  other  hand,  the  tears  serve 
to  lubricate  the  respiratory  organ,  and  to  counteract  the  dry- 
ing effect  caused  by  inhalations  of  dry  air;  the  entrance  to 
the  air-tubes  is  moistened  by  means  of  the  vapor  which  is 
given  off"  in  the  air  inhaled,  and  the  tears  apparently  assist  in 
maintaining  that  state  of  moisture  in  the  lungs  which  is  so 
favorable  to  the  exchange  of  the  gases  (L.  Bergeon).  The 
lachrymal  system,  the  product  of  which  always  flows  into  the 
nostrils,  is  found  even  in  the  ophidia,  although  their  eyeball 
being  hidden  behind  the  tegumentary  system,  is  completely 
beyond  the  influence  of  evaporation.  On  the  other  hand, 
animals,  such  as  the  cetaceans,  which  continually  breathe  an 
air  saturated  with  moisture,  are  the  only  ones  without  lachry- 
mal glands.^ 

^  See  A.  Estor,  "  Physiologie  Pathologique  des  Fistules  Lacry- 
males,"  in  "  Journ.  de  I'Anat.  et  de  la  Physiol.,"  by  Ch.  Robin. 
Janvier,  1866. 


PART    TENTH. 


TJRO-GENITAL  APPARATUS.  —  EMBRY  OLOGY. 


Origin  and  Development  of  the  Uro-G:enital 
Apparatus. 


The  uro-genital  mucous  surface  and  its  appendages,  on 
their  first  appearance,  are  only  a  portion  of  the  alimentary 
canal,  of  the  mucous  layer  of  the 
Uastoderma.  At  the  period  when 
the  intestinal  canal  exists  only  in 
the  form  of  a  tube,  its  middle  por- 
tion communicates  with  the  ger- 
minal vesicle,  and  each  end  termi- 
nates in  a  cul-de-sac ;  on  its  lower 
part  may  be  seen  a  protuberance 
(B),  (Fig.  124),  and  a  partition 
(E)  which  separates  the  primitive 
tube  from  the  later  protuberance; 
-ji  in  this  protuberance,  which  becomes 
more  and  more  prominent,  may  be 
found  two  cavities:  1.  The  older 
cavity  of  the  digestive  tract  or 
^.'•^•^H7;^^^^^"'*?f^^®^*'™'^;tube,  which  will  later  become  the 

tion  of  the  uro-genital  organs.*  '  i   ^    t      ^ 

rectum;  and,  2.  In  iront  a  uro-gem- 
tal  cavity  or  sinus  uro-genitalis^  from  which  are  formed 
every  part  of  the  urinary  and  genital  organs. 

*  1.  I,  I,  Intestinal  tube,  with  the  protuberance  B,  which  will  soon  be  sepa- 
rated bv  the  partition  E. 

2.  The  partition  has  extended ;  the  protuberance  B  is  very  much  developed, 
and  has  given  place  to  the  allantois  A  (the  commencement  of  which,  the  pedicle, 
can  only  be  seen),  and  successively,  proceeding  from  the  allantois  towards  the 
intestinal  tube,  the  urachus  O,  the  bladder  V,  the  genito-urinary  sinus  SU,  which 
has  also  given  off  three  protuberances:  for  the  Wolffian  body  1,  for  the  duct 
of  Miiller  2,  and  for  the  kidney  3. 


URO-GENITAL  SYSTEM.  459 

In  fact  this  nro-genital  sinus  (beside  the  allantols,  Fig. 
124,  A,  that  we  shall  examine  further  on)  gives  origin  to 
three  protuberances  or  ccBca  on  each  side  ;  these  elongate  in 
'he  direction  of  the  superior  portion  of  the  germinal  vesicle. 

1.  The  first  of  these  protuberances,  or,  more  properly  speak- 
ing, germs  (Fig.  124,  1),  itself  gives  rise  to  lateral  vegeta- 
tions, from  which  a  penniform  organ  is  formed ;  this  is  the 

Wolffian  hody^  which  in  foetal  life  is  developed  to  a  great 
size  and  occupies  the  largest  portion  of  the  abdominal  cavity. 
At  this  same  period  it  comprises  elements  analogous  to  the 
glomervli  or  corpuscles  of  Malpighi  in  the  kidney,  and  seems 
to  possess  the  same  functions  that  afterwards  belong  to  this 
latter  organ ;  in  consequence  of  which  function  the  Wolffian 
body  has  been  called  the  primordial  kidney  (Jacobson, 
Rathke).  But,  towards  the  close  of  the  first  half  of  foetal 
life  in  the  female  foetus,  these  organs  become  atrophied  and 
disappear,  whilst,  on  the  other  hand,  a  portion  of  the  male 
genital  organs  is  developed  from  them. 

2.  The  second  protuberance  or  caecum  elongates  without 
presenting  secondary  vegetations ;  this  forms  a  single  tube 
known  by  the  name  of  Mullerian  duct  or  organ  of  Miiller 
(Fig.  124,  2).  This  is  essentially  arranged  for  the  formation 
of  the  most  important  portions  of  the  female  genital  organs, 
Fallopian  tubes  and  uterus ;  in  man  they  form  comparatively 
useless  rudimentary  vestiges  of  the  embryonic  state,  such 
as  the  utriculus  j^^ostaticus  (prostatic  vesicle),  and  a  small 
appendage  of  the  epididymis,  the  corpora  Morgagnii,  hyda- 
tids of  Morgagni. 

3.  The  third  protuberance  or  caecum  (Fig.  124,  3)  presents 
quite  a  number  of  secondary  vegetations,  originating  and 
radiating  from  the  end  of  the  tube.  These  secondary  pro- 
tuberances assume  the  form  of  canaliculi  placed  side  by  side, 
interlace  and  finally  converge  in  a  little  vascular  tuft,  against 
which,  as  it  were,  their  extremity  abruptly  terminates  in  a 
caecum ;  beyond  this  point  they  are  not  developed.  Each  of 
these  embraces,  by  its  csecal  extremity,  a  vascular  tuft ;  this 
latter  fills  up  the  interior  of  the  hollow  of  the  cul-de-sac  in 
such  a  way  as  to  be  lodged  in  a  terminal  capsule.  Thus  are 
formed  the  uriniferous  tubes  and  the  malpighian  corpuscles 
{glomeruli  Malpighii),  in  one  word,  the  kidney. 

Finally,  beyond  these  three  protuberances  on  each  side,  the 
anterior  extremity  of  the  uro-genital  simis  is  developed,  and 
constitutes  the  allantoid  canal  {urachus)  and  the  allantoid 
bladder  (vesicula  allantoidiana,  Fig.  124,  0,  A),  whose  func- 


460  URO-GENITAL  SYSTEM. 

tions  we  shall  presently  study  when  we  consider  the  placent  u 
We  will  in  this  place  only  mention  that  the  allantois  and  its 
canal,  the  urachus,  both  disappear  in  the  adult.  The  inferior 
portion  of  the  canal  alone  remains,  and  being  developed 
to  an  enormous  size,  constitutes  the  reservoir,  called  the 
bladder. 

This  rapid  review  of  the  origin  of  the  genital  and  urinary 
organs  exhibits  a  close  relationship  between  these  two  sys- 
tems, and  consequently  teaches  the  close  analogy  between 
their  epitheliums ;  since  these  mucous  surfaces  always  origi- 
nate from  the  epithelium  of  the  sinus  uro-genitalis^  which 
latter  is  an  offshoot  from  the  intestinal  epithelium^  that  is, 
the  internal  layer  of  the  blastoderm. 

We  shall  study  in  succession  the  urinary  system  and  the 
genital  system  of  the  male  and  the  female.  We  shall  else- 
where recur  to  the  embryological  conditions  of  the  two  latter, 
which  alone  furnish  facts  that  establish  the  homology  of  the 
organs  of  the  two  sexes. 

I.    URINARY  APPARATUS. 

A.  Secretion  of  urine. 

In  their  structure  the  canals  or  tubes  which  compose  the 
renal  parenchyma  resemble  the  sudoriferous  glands.  These 
are  straight  tubules  in  the  medullary  portion  of  the  kidney 
(ducts  of  Bellini,  Fig.  125),  then  becoming  convoluted  or 
twisted  together  (ducts  of  Ferrein)  in  the  cortical  substance.^ 

^  The  connections  of  the  straight  tubules,  of  the  convoluted 
tubules  (tuhuli  contorti),  and  of  the  glomeruli  (Malpighian  cor- 
puscles) of  the  kidney,  especially  demonstrated  by  Schumlansky, 
Bowman,  and  Isaacs,  have  met  with  formidable  antagonism  from 
Miiller  and  Henle.  Henle  especially  has  undertaken  to  describe 
some  looped  tubules  among  the  uriuiferous  tubes,  which  he  con- 
sidered as  terminating  in  culs-de-sac,  or  dividing  into  smaller 
tubuli.  There  are,  indeed,  very  remarkable  looped  tubules  in  the 
kidney,  but  a  study  of  these  tubules,  called  tubules  of  Henle, 
undertaken  by  Kblliker,  Zawarickin,  and  especially  Schweigger- 
Seidel,  has  demonstrated  that  these  formed  no  separate  system,  as 
was  formerly  supposed  by  Henle  (see  "  Traite  d' Anatomic,"  by 
Cruveillier  and  M.  See.  4th  edition,  1869).  By  the  action  of 
acids  on  the  substance  of  the  kidney,  Schweigger-Seidel  was  the 
first  to  show  that  Heule's  tubules  have  the  most  intimate  connection 
with  the  classical  straight  and  convoluted  tubules  of  the  kidney,  and 
that  they  are  not  in  the  least  degree  blood-vessels,  as  Chrzon- 


URINARY  SYSTEM. 


461 


At  this  point  each  of  these  terminates  in  a  sac-like  dilatation 
into  which  projects,  hernia-liJce,  a  vascular  tuft  {glomerulus 
Malpighii),  formed  by  the  capillarization   of  an   arteriole 


Pig.  125.  —  Tubuli  of  the  kidney .* 

{afferent  vessel).  Fig.  125,  a.  These  capillary  tufts  converge 
to  form  a  small  efferent  vessel  which  leaves  the  glomerulus  at 

sczewsky  and  Sucquet  tried  to  prove.  These  looped  tubules  (going 
froDi  the  glomeruli  towards  the  medullary  substance  of  the  kidney, 
and,  in  fact,  following  the  same  course  as  the  urine)  are  continua- 
tions of  the  tubes  of  Ferrein,  whose  walls  at  a  certain  place  become 
much  smaller,  rectilinear,  and  descend  in  the  medullary  substance 

♦  Origin  and  dichotomy  of  the  uriniferous  canaliculi  in  the  medullary  sub- 
stance of  the  human  kidney  (tubes  of  Bellini).     (Schumlansky.) 


4G2 


URO-GENITAL  SYSTEM. 


the  same  or  near  the  point  where  the  afferent  vessel  enters 
(Fig.  1 26,  p  Y).  But  it  must  be  noted  that  the  efferent  vessel 
does  not  immediately  reunite  with 
its  fellows  to  form  the  renal  vein ; 
almost  immediately  after  it  has  left 
the  glomerulus  it  divides  again  and 
forms  a  capillary  system  in  the  renal 
parenchyma  (RC),  the  vascular  net- 
work of  which  interlaces  with  the 
uriniferous  tubes.  This  efferent  ves- 
sel does  not  merit  the  name  of  a 
vein ;  it  belongs  to  a  separate  sys- 
tem which  we  might  perhaps  con- 
sider as  a  renal  portal  vein,  since  it 
is  intermediate  between  two  capil- 
lary systems,  viz.,  the  glomeruli  and 
the  renal  parenchyma  ;  the  true  ori- 
gin of  the  renal  vein  is  subsequent 
to  these  last-named  capillaries. 

This  arrangement  of  the  vascular 
system  in  the  kidney  forms  the  basis 
of  all  the  modern  theories  upon  the  urinary  secretion;  Vi  filtra- 
tion is  the  fundamental  process  on  which  these  theories  depend. 
If  we  recall  the  fact  that  differences  of  pressure  between 
the  various  parts  of  the  circulatory  system  do  not  bear  any 
relation  to  the  especial  form  of  these  parts  (trunks,  small 
vessels,  or  capillaries),  but  to  their  distance  from  two  extreme 
points  (left  ventricle  and  right  auricle)  of  the  origin  andter- 

of  the  pyramids  of  Ferrein  (alongside  of  the  tubules  of  Bellini), 
then  reascend  again,  becoming  larger,  and  go  into  the  cortical  sub- 
stance; there  these  tubes  take  a  new  direction,  and  finally  continue 
with  the  true  tubes  of  Bellini.  In  brief,  the  tubes  of  Henle  become 
loops  in  form  of  inverted  siphons  between  the  tube  of  Ferrein  and 
that  of  Bellini.  The  only  physiological  knowledge  that  we  at 
present  possess  of  these  looped  tubes  is  dependent  on  their  constric- 
tion in  the  descending  branches,  and  the  dilatation  in  their  ascend- 
ing branches.  Yet  their  epithelium  is  clear  and  transparent  in  the 
straight  and  descending  branch,  turbid  and  granular  in  the  large 


Fig.  126.  —  Diagram  of  the  kid 
ney  and  its  circulation.* 


and  descending  portion  (towards  the  bases  of  the  pyramids).    (See 
I.  Fr.  Gross,  "  Essai  sur  la  Structure  Microscopique  du  Rein." 


Ch. 


These  de  Strasbourg,  1808,  No.  95.) 

*  TZ>,  Straight  tube  of  Bellini.  T/*,  Convoluted  tube  of  Ferrein.  G,  Glom- 
erulus, with  its  vascular  tuft,  a.  Afferent  arteriole,  going  to  the  capillaries  of 
the  corpuscle.  pY,  Efferent  vessel  forming  smaller  capillaries  among  the  renal 
tiibuli  m  KG,  before  forming  the  true  venous  vessel  V. 


URINARY  SYSTEM. 


463 


niination  of  the  vascular  apparatus,  we  can  then  readily 
understand  that,  in  the  two  systems  of  renal  capillaries,  the 
pressure  will  not  vary  from  that  of  the  ordinary  capillary 
8ystem  (of  the  limbs,  for  instance).  Whilst  (Fig.  127)  in 
these  last,  on  account  of  their  intermediate  position  (see 
Circulation,  p.  151)  between  the  origin  of  the  arterial  cone 
jind  the  termination  of  the  venous  cone,  the  pressure  is 
also  intermediate  between  the  two  corresponding  extreme 
pressures ;  that  is,  this  pressure  may  be  represented  by  -^^^ 
(that  at  the  origin  of  the  aorta  =  ^y%,  and  that  of  the  ter- 
mination of  the  vena  cava  =  0  or  yi^)  ;  this  is  not  so  in  the 
renal  system ;  for  this  number  ^^  represents,  not  the  pressure 
of  either  of  the  two  kinds 
of  capillaries,  but  the  pres- 
sure of  the  efferent  trunk 
of  the  glomerulus  (of  the 
vessel  pY  in  Fig.  126); 
because,  as  shown  by  the 
diagram  (Fig.  127,  2)  it  is 
this  efferent  trunk  (S  P) 
which  is  placed  midway 
between  the  distance  of 
the  left  ventricle  (V)  and 
the  right  auricle  (O). 

As  for  the  pressure  in 
the  renal  capillaries,  a  similar  calculation  will  sho,/  that  in  the 
glomerulus,  that  is,  in  those  capillaries  which  are  placed  between 
the  arterial  system  properly  so  called  and  the  efferent  vessel 
(S  P,  Fig.  127),  the  pressure  should  be  intermediate  between 
■^^^  and  ^J^^,  viz.,  -^^q.  In  those  capillaries  which  Ibllow  the 
efferent  vessels  which  wind  about  the  urinit'erous  tubes  to 
give  origin  to  the  vein  properly  so  called  (Fig.  126,  RC)  and 
(Fig.  127,  C'C),  the  pressure  should  be  intermediate  between 
-j^jpQ  and  ji^,  or  equal  to  j§^  (see  Circulation,  p.  151). 


Fig.  127.  —  Diagram  of  the  two  capillary  sys- 
tems in  the  kidney  or  the  renal  portal  vein.* 


*  The  superposition  of  the  numerals  show  that  the  pressures  are  not  the 
sj'me  in  the  capillary  sjstem  of  the  general  circulation  and  in  each  of  the  capil- 
lary systems  of  the  kidneys  (at  the  glomerulus,  and  in  the  interstices  of  the 
tubes). 

1,  General  circulation.  V,  Ventricle.  0,  Auricle,  a,  Arterj'.  V,  Veins. 
CC,  Capillaries  (pressure,  12). 

2.  Renal  circulation.  V,  Ventricle.  O,  Auricle,  a.  Renal  artery  and  affer- 
ent vessel  of  the  glomerulus.  c\  (/,  Capillaries  of  the  glomerulus  (pressure,  18). 
3P,  Efferent  vessels  of  the  glomerulus  (representing  the  trunk  of  a  poital  vein, 
the  vessel  pV  of  Fig.  126).  c,  c.  Capillaries  resulting  from  the  dichotomy  oi 
this  efferent  trunk  amongst  the  renal  tubes  (pressure,  6).  v,  Renal  vein,  cor- 
rectly called,  following  this  second  system  of  capillaries. 


464  URO-GENITAL  SYSTEM. 

In  a  general  way,  then,  it  may  be  said  that  the  blood  of  the 
capillaries  in  the  glomertdus  is  subjected  to  quite  a  consider- 
aJble  pressure^  and  that  in  the  interstitial  or  parenchymatous 
capillaries  there  exists  a  pjressure  less  than  that  of  the  blood 
in  the  ordinary  capillaries. 

The  intensity  of  the  pressure  in  the  first  system  has 
attracted  the  attention  of  every  physiologist,  and  all  admit 
that  in  this  system  there  should  occur  a  mechanical  filtration 
which  would  be  the  first  jDhase  of  the  source  of  the  urinary 
secretion,  but  there  is  a  want  of  agreement  with  regard  to 
the  character  of  the  liquid  filtered.  Some  (Bowman)  con- 
sider that  it  is  simply  water;  others  (Ludwig)  that  it  is 
urine,  but  largely  diluted,  which  by  the  loss  of  a  portion  of 
its  water  will  become  the  urine  that  is  afterwards  poured 
into  the  bladder.^ 

If  we  apply  here  the  information  that  physiology  of  the 
capillaries  of  other  portions  of  the  body  has  supplied,  and 
recollect  that  the  capillaries  of  the  glomerulus  present  a 
structure  similar  to  those  of  every  other  region ;  we  ought  to 
conclude  that  in  these  capillaries  there  is  normally  produced, 
in  view  of  the  normal  and  permanent  excess  of  the  pressure, 
what  is  abnormally  produced  in  every  other  region  when  the 
blood  pressure  is  exaggerated.  Following  out  this  sugges- 
tion, when  a  ligature  compresses  the  veins  of  the  foreami, 
when  from  a  pathological  cause  the  abdominal  venous  circu- 
lation is  arrested ;  in  brief,  at  any  time  that  the  pressure  in 
the  capillaries  is  increased,  these  latter  will  allow  the  liquid 
portion  of  the  blood  to  filter  out  through  their  walls,  with  all 
the  constituent  elements  of  the  serum,  viz.,  water,  albumen, 
etc.  The  supposition  is,  then,  authorized  that  the  same  phe- 
nomenon will  occur  in  the  glomerulus,  and  that  this  latter 
does  not  allow  pure  water,  but  the  serum  of  the  blood  with- 
out making  any  distinction  between  its  elements,  to  pass  into 
the  uriniferous  tube. 

This  view  is  fully  confirmed  by  an  experiment  already  per- 
foniied  in  nature  by  pathology :  when  an  uriniferous  tube,  in 
any  part  of  its  course,  becomes  obliterated,  its  initial  portion 
continues  to  receive  the  products  of  filtration  in  the  glomer- 
ulus which  have  accumulated  in  the  obliterated  portion ;  this 
latter  enlarges,  and  finally  forms  a  cyst  of  variable  size. 
Now  if  the  contents  of  similar  cysts  be  analyzed,  these  are 

^  See  CI.  Bernard,  "  Lemons  sur  les  Liquides  de  1' Organisme. " 
Vol.  II.  Legon  0. 


URINARY  SYSTEM.  465 

found  to  consist  of  a  liquid  identical  with  the  serum  of  the 
blood :  this  proves  that  the  serum  filters  out  in  the  glom- 
eruli. 

This  is  the  first  phenomenon  of  the  secretion  of  urine :  fil- 
tration of  the  serum  of  the  blood. 

We  will  now  learn  how  the  product  of  filtration  in  the 
glomeruli  is  transformed  into  urine :  this  transformation  evi- 
dently occurs  in  the  sinuous  course  of  the  uriniferous  tubes 
(tuhuli  uriiiiferi)^  througli  which  the  filtered  liquid  is  carried 
from  its  original  point  to  the  pelvis  of  the  kidney. 

Those  authors  who  see  in  the  filtered  liquid  simply  pure 
water  cnnuot  conceive  the  formation  of  urine  except  by  a 
secretion  from  the  walls  of  the  uriniferous  canaliculi,  a  secre- 
tion to  which  is  added  the  substances  that  the  urine  should 
contain.  On  the  other  hand,  those  who,  like  Wittich  and 
ourselves,^  see  in  the  filtered  product  a  very  diluted  urine, 
believe  that  the  formation  of  the  urine  is  accomplished  by  a 
simple  aqueous  reabsorption,  effected  by  the  medium  of  the 
uriniferous  tubes,  thus  giving  to  the  urine  the  desired  con- 
centration. 

As  we  have  demonstrated  that  the  product  of  the  filtration 
in  the  glomeruli  is  the  serum  of  the  blood ;  and  as  a  compara- 
tive study  of  the  composition  of  both  serum  and  urine  shows, 
in  a  general  manner,  that  in  the  composition  of  the  two 
liquids  the  serum  differs  from  the  urine  07ily  by  the  p>resence 
of  albumen  j  we  are  induced  to  believe  that  the  formation  of 
urine  consists  in  the  absorption  of  this  albumen^  an  absorp- 
tion that  necessarily  occui-s  along  the  circuit  of  the  uriniferous 
tubes. 

This  explanation  of  de,  second  phase  of  the  worJc  of  the 
kidneys  is  a  necessary  consequence  of  the  theory  advanced 
in  the  earlier  portion  of  this  book ;  it  is  true  that  there  is  no 
way  by  which  we  can  verify  the  theory ;  but  we  may  be 
allowed  to  examine  whether  what  we  know  of  the  structure 
of  the  kidneys  is  favorable  to  this  view. 

In  the  first  place,  the  length  and  the  form  of  the  convoluted 
tubes,  a  form  so  closely  resembling  the  intestinal  convolu- 
tions, naturally  leads  to  the  theory  that  we  have  also  in  the 
kidneys  a  system  or  apparatus  for  absorption,  and  in  which 
the  course  of  the  liquid  is  retarded  for  the  purpose  of  favor- 

'  V.  Wittich,  Virchow's  "  Archiv  fur  Pathologische  Anat- 
omie."  Vol.  X.  — Donders,  "  Physiologie  des  Menschen."  Leip- 
zig, 1859,  Vol.  I. 

SO 


466  URO-GENITAL  SYSTEM. 

ing  a  prolonged  contact  with  the  walls  of  the  tubes.  In  the 
second  place,  the  lining  epithelium  throughout  the  principal 
part  of  these  tubes  is  clear  and  transi)arent,  unlike  the  gran- 
ular epithelium  of  the  secreting  glandular  sacs;^  and  more- 
over, whilst  this  latter  reveals  its  function  by  the  numerous 
cellular  detritus  that  are  found  in  the  secreted  liquid  (since 
in  a  general  way  it  may  be  stated  that  every  secretion  of  this 
kind  is  the  result  of  a  desquamated  epithelial  moulting)  ;  on 
the  contrary,  the  epithelium  of  the  uriniferous  tubes  shows 
little  if  any  of  this  detritus,  the  urine  being  a  liquid  which  is 
very  poor  in  globular  elements.  This  epithelium  thus  appears 
destined  to  preside  over  an  absorption,  and  undoubtedly  does 
so  in  an  active  manner,  by  removing  from  the  serum  an  ele- 
ment so  essential  to  the  organism,  and  of  which  the  blood  can- 
not be  deprived  without  risk,  viz.  albumen.  Should  this 
epithelium  become  diseased,  it  will  no  longer  fulfil  its  func- 
tion, and  albumen  will  not  be  absorbed,  but  will  appear  in 
the  urine;  this  latter  accident  occurs  in  Bright's  disease, 
which  is  precisely  a  disease  of  the  kidney  epithelium.  Those 
writers  who  would  allow  for  this  epithelium  a  function  of 
secretion,  by  means  of  which  the  wall  of  the  tube  would  add 
to  the  filtered  water  the  constituent  elements  of  urine,  find 
themselves  in  face  of  a  singular  contradiction  when  they 
desire  to  explain  the  pathogeny  of  albuminuria;  because,  as 
a  necessary  result  of  their  theory,  when  this  epithelium  is 
diseased,  it  must  secrete,  not  only  the  solid  matters  which 
normally  belong  to  the  constitution  of  urine,  but  in  addition 
to  these  a  new  element,  albumen :  thus  we  should  have,  as 
the  sole  example  in  the  organism,  this  epithelium  performing 
its  function  with  more  activity  in  a  diseased  than  in  a  normal 
state;  producing  all  the  elements  belonging  to  its  normal 
condition,  and  others  besides.^ 

We  know  already  that  a  feeble  pressure  in  the  blood- 
vessels conduces  to  a  favorable  absorption  (see  p.  273).  We 
have  also  seen  that  in  the  capillaries  which  are  near  the  uri- 
niferous tubes  the  pressure  is  less  than  in  the  ordinary  capil- 
laries.     The  interstitial  network   of  blood-vessels   is  then 

'  See  the  note  on  p.  533. 

*  These  considerations  of  pathology,  which  belong  to  the  theory 
of  urinary  secretion,  as  we  have  just  evolved,  have  been  lately  de- 
veloped, especially  in  relation  to  albuminuria,  in  a  thesis  by  G. 
Fayet:  "  Essai  sur  la  Pathogenic  de  1' Albuminuric. "  Montpellier, 
1872.  See,  also,  J.  B.  Olinger,  "  Esquisse  de  la  Physiologie  de  la 
Fonction  Urinaire."     Paris,  1873,  No.  84. 


URINARY  SYSTEM.  467 

admirably  arranged  to  receive  the  albumen  reabsorbed  by  the 
epithelium;  and  so,  too,  are  the  capillaried  of  the  malpighian 
tufts  (the  glomeruli)  arranged  to  allow  a  filtration  of  the 
serum ;  in  fact,  it  is  owing  to  this  circulatory  system,  which 
we  have  called  the  renal  portal  vein,  that  the  solution  of  this 
twofold  phenomenon  may  be  found,  viz.  filtration  and  re- 
absorption,  which  constitute  the  two  phases  essential  to  the 
secretion  of  urine.  Comparative  physiology  illustrates  this 
twofold  phenomenon  still  more  perfectly :  among  the  ophid- 
ians (snakes,  etc.),  which  secrete  a  solid  urine,  a  liquid  is 
found  at  the  beginning  of  the  uriniferous  tubes,  which  gradu- 
ally becomes  thickened  in  its  course,  until  it  finally  acquires 
the  characteristic  semi-solid  consistency. 

Thus,  to  sum  up,  the  secretion  of  urine  is  composed  of  two 
distinct  phases:  1,  A  phenomenon  of  simple  filtration  in  the 
glomerulus;  2,  To  this  purely  mechanical  phenomenon  there 
succeeds  a  vital  work  on  the  part  of  the  globular  elements  of 
the  epithelium  of  the  uriniferous  tubes. 

This  epithelium  of  the  uriniferous  tubes,  then,  simply  ab- 
sorbs, but  does  not  secrete ;  formerly  it  was  supposed  to  have 
something  to  do  with  the  formation  of  urea,  but  it  is  now 
proved  that  all  the  urea  found  in  the  urine  is  primarily  con- 
tained in  the  blood.  The  origin  of  urea  in  the  kidney  is  re- 
duced to  a  simple  question  of  experiments,  the  results  of 
which  show  that  urea  pre-exists  in  the  blood,  and  is  not 
formed  in  the  kidney;  that  the  blood  of  the  renal  vein  nor- 
mally contains  less  urea  than  that  in  the  renal  artery ;  that 
ligation  of  the  ureters  produces  the  sume  symptoms  as  abla- 
tion of  the  kidneys.  In  France,  Provost  and  Dumas,  Segalas 
and  Vauquelin,^  CI.  Bernard  and  Barreswil,  Picard^  (These 
de  Strasbourg,  1856),  have  arrived  at  these  results;  yet,  in 
Germany,  their  researches  have  been  opposed  on  account  of  an 
assumed  error  in  the  estimation  of  urea;  Oppler,  Perls,  Her- 
mann, Hoppe-Seyler,  and  Zalesky  contend  that  a  large 
amount  of  urea  is  formed  in  the  renal  tissue,  just  as  ptyaline 
is  formed  in  the  salivary  glands  ;  a  maceration  of  kidney  gives 
origin  to  urea  in  the  same  way  that  a  maceration  ®f  the 
parotid  gland  gives  rise  to  animal  diastase.  Finally,  Zalesky 
pretends  that  ablation  of  the  kidneys  (nei)hrotomy)  and  liga- 
tion of  the  ureter  produce  different  symptoms ;  that,  after 

*  Journal  de  Magendie.     Vol.  II.  p.  351. 

2  J.  Picard,  "  Do  la  Presence  de  1' Urine  dans  le  Sang  et  de  sa 
Diffusion  dans  POrganisme." 


468  URO-GENITAL  SYSTEM. 

ligature  of  the  ureter,  urea  is  found  in  much  greater  abun- 
dance in  the  blood,  and  more  rapidly  induces  uraemic  poison- 
ing. This  question  has  been  decided  by  the  employment  of 
an  incontestable  means  of  estimating  the  amount  of  urea,  viz. 
by  the  process  employed  by  Grehant :  with  Millon's  reagent, 
or  the  nitrous-nitrate  of  mercury,  the  urea  is  decomposed  into 
equal  volumes  of  carbonic  acid  and  nitrogen ;  the  especial 
precision  and  characteristic  feature  of  this  process  depends 
upon  the  collection  of  all  the  carbonic  acid  and  all  the  nitro- 
gen, that  is  produced  by  this  reaction,  in  such  a  manner 
that  in  each  analysis  the  equality  of  the  determined  volumes 
of  carbonic  acid  and  nitrogen  will  render  certain  that  only 
urea  has  been  decomposed.  In  this  way  it  has  been  demon- 
strated, that  the  accumulation  of  urea,  after  the  operation  of 
nephrotomy,  occurs  in  a  continuous  manner ;  and  that  in  this 
case,  as  after  ligation  of  the  ureters,  the  quantity  of  urea 
which  accumulates  in  the  blood  is  equal  to  the  amount  that 
the  kidneys  would  excrete ;  that  after  ligation  of  the  ureters, 
the  blood  which  leaves  the  kidney  contains  exactly  the  same 
amount  as  that  which  enters  this  organ  ;  that  in  the  normal 
condition  of  the  blood  the  renal  vein  contains  less  urea  than 
the  renal  artery,  and  that  this  deficit  precisely  corresponds 
with  the  quantity  of  urea  which  is  thrown  off  by  the  urine  ^ 
during  the  same  period  of  time.  We  have  then  the  right  to 
conclude  in  an  incontestable  manner,  that  the  kidney  is 
simply  a  filter,  in  which  urea  is  eliminated,  that  is,  the  renal 
filter  can  be  impregnated  with  this  substance  and  give  it  up 
by  drainage. 

B.   Composition  of  urine. 

Urine  is  secreted  during  24  hours  in  variable  quantity,  in 
the  normal  condition  to  the  amount  of  500  to  1500  grammes. 
This  urine  is  an  aqueous  solution  of  various  principles :  its 
elements  in  solution  are  pretty  constant  in  quantity,  the 
variation  being  due  to  the  proportion  of  water;  in  fact, 
the  urine  is  more  or  less  abundant  during  health,  because  it 
may  be  more  or  less  diluted. 

The  quantity  of  water  in  the  urine  depends  upon  the  con- 
ditions of  the  circulation  and  blood;  as  the  urinary  secretion 
is  a  filtration  resulting  from  pressure,  when   the  arterial 

*  See  Grdhant,  "  Cours  de  I'Ecole  Pratique  de  la  Faculte  de 
Medecine  de  Paris."  ("  Kevue  des  Cours  Scientifiaues."  Nov., 
1871.) 


URINARY  SYSTEM.  469 

tension  increases,  more  urine,  or,  correctly  speaking,  more 
water  will  be  excreted ;  so  also  when  the  arterial  tension  is 
diminished,  the  urine  will  be  less  abundant.  Physicians 
know  full  well  that  there  is  no  necessity  for  prescribing 
diuretic  medicines  for. patients  whose  pulse  is  very  soft  and 
feeble,  and  that  in  such  cases  the  best  diuretic  will  be  a  drug 
that  will  stimulate  the  force  of  the  heart  and  the  circulation. 
With  this  understanding  the  urinary  secretion  is  very  im- 
portant, for  it  forms  a  sort  of  safety-valve  by  means  of  which 
the  blood  is  freed  of  an  excess  of  water.  After  a  meal  there  is  a 
sort  of  general  plethora,  an  augmentation  of  the  blood  tension, 
and  consequently  an  abundant  and  diluted  urine  will  flow 
{iirina  potus  et  cibi).  In  the  morning,  however,  the  urine 
secreted  during  a  previous  night  of  repose  is  more  concentrated 
and  scanty,  because  there  has  been  no  cause  to  increase  the 
quantity  of  liquid  in  the  blood  nor  its  pressure.  The  lungs 
eliminate  a  slight  amount  of  water.  A  proportion  between 
the  weight  of  the  organism  and  the  quantity  of  solid  residue 
contained  in  the  daily  urine  may  be  calculated.  Each  kilo- 
gramme of  the  weight  of  the  animal  is  represented  by  one 
gramme  of  anhydrous  urine.  Yet  this  proportion  may  vary 
according  to  the  season  or  character  of  food. 

A  man  weighing  65  kilos,  will  excrete,  on  an  average,  65 
grms.  of  anhydrous  urine.  Nearly  one-half  (30  grms.)  of  the 
anhydrous  daily  urine  is  represented  by  a  substance,  urea, 
that  we  have  mentioned  before  when  speaking  of  all  of  the 
other  liquids  of  the  organism.  This  substance  is  a  nitrogen- 
ous principle.  More  nitrogen  is  eliminated  in  urea  than  in 
any  other  excrementitial  product.  It  has  been  demonstrated 
that  the  urea  excreted  is  almost  all  (according  to  Lehmann, 
four-fifths)  that  which  can  be  produced  from  the  food  we  eat ; 
the  remaining  one-fifth  may  be  accounted  for  when  we  recol- 
lect that  the  respiratory  excretion,  as  well  as  the  epidermal 
exfoliation  and  the  secretion  of  sweat,  contain  a  small  amount 
of  urea.  There  is  also  found  in  the  urea  about  one-fifth  of 
the  carbon,  which  must  be  added  to  the  500  grms.,  that  we 
daily  excrete  by  means  of  the  lungs. 

The  amount  of  urea  may  vary  under  the  influence  of  cer- 
tain well-defined  conditions ;  since  it  is  the  residue  from  the 
combustion  of  albuminoids  in  the  organism,  its  abundance 
will  depend  upon  the  amount  of  animal  food  contained  in 
nutriment. 

In  a  general  way  it  may  be  stated  that  there  is  a  direct 


470  URO-GENITAL  SYSTEM. 

ratio  between  the  degree  of  animal  heat  and  the  amount  of 
urea  eliminated  (Hepp  and  Hirtz).^ 

The  remaining  35  grms.  of  anhydrous  urine  (half  the 
amount  eliminated  in  a  day)  is  distributed  as  follows : — 

There  are  15  grms.  of  matters  called  extractive,  that  is, 
products  of  incomplete  combustion  of  the  albuminoids :  to 
this  class  belong  creatine^  creatinine,  etc.,  but  the  most  inter- 
esting of  this  class  is  uric  acid,  not  found  in  large  quantity, 
it  is  true;  but  which,  under  certain  circumst-ances,  can  be 
accumulated  to  a  large  extent,  or  be  retained  in  the  tissues 
(uric  acid  diasthesis ;  gout;  ^ojoAws  of  urate  of  soda).  In  the 
normal  state  this  substance  exists  in  proportion  to  the  urea, 
as  1  is  to  30 ;  that  is  to  say,  that  1  grm.  is  found  in  the  urine 
of  24  hours.  Its  especial  characteristic  consists  in  its  sparing 
solubility  in  water,  which  dissolves  only  ^^^  of  its  weight. 
On  account  of  its  difficult  solubility  we  cannot  explain  how 
uric  acid  exists  in  solution  in  the  urine ;  it  may  be  in  com- 
bination with  soda  as  urate  of  soda;  yet,  as  this  latter  is 
scarcely  any  more  soluble  than  uric  acid  (yoW)'  ^^'®  must 
suppose  that  uric  acid  or  the  urates  are  dissolved  by  the  aid 
of  the  acid  phosphate  of  soda  (that  which  gives  to  urine 
its  acid  reaction),  or  by  that  of  the  coloring  matter.  It  is 
known  that  if  urine  be  allowed  to  stand  while  exposed  to  the 
air,  a  species  of  lactic  acid  fermentation  ensues,  by  which  a 
large  portion  of  the  coloring  matter  seems  to  be  destroyed 
and  uric  acid  to  be  formed.  Among  many  of  the  herbivora 
an  analogous  acid,  hippiiric  acid,  apparently  replaces  the  uric 
acid;  this  former  acid  is  composed  of  benzoic  and  glyco- 
cholic  acid :  in  fact,  man  can  make  this  acid  appear  in  his 
urine  by  the  ingestion  of  benzoic  acid ;  glycochol  or  sugar  of 
gelatine  is  by  this  means  provided  by  the  metamorphosis  of 
the  connective  tissue. 

There  now  remain  but  20  grms.  of  anhydrous  urine  for 
whose  composition  we  must  account ;  these  20  grammes  are 
represented  by  the  salts,  of  which  chloride  of  sodium  forms 
8  parts,  and  various  other  salts  12  parts  (sulphates,  phos- 
phates, lactates,  &c.).  The  base  of  these  salts  is  mostly  soda ; 
there  are  also  some  salts  of  lime  held  in  solution  by  means  of 
an  excess  of  acid.  Alkaline  urine,  as  from  the  herbivora, 
for  instance,  is  turbid ;  and  horse-urine  is  employed  as  a  type 

'  See  Art.  "  Fievre,"  in  Vol.  XVI.  of  the  "  Nouveau  Diet,  de 
M^decine  et  de  Chirurgie  Pratiques." 


URINARY  SYSTEM.  471 

for  the  designation  of  urine  which  is  turbid  or  alkaline  owing 
to  some  pathological  cause,  hence  c^Wad  jumentous  nruie. 
The  phosphates  are  usually  made  up  of  the  alkaline  earthy- 
salts,  there  being  in  the  urine  passed  during  24  hours  about 
one  or  two  grms.  of  phosphate  of  lime  and  magnesia.  It  is 
worthy  of  note  that  the  kind  of  alimentation  has  a  certain 
influence  upon  the  presence  of  the  phosphates  and  sulphates 
in  the  urine  ;  we  usually  take  but  a  small  quantity  of  sulphur 
and  phosphorus  as  contained  in  the  organic  products  (albu- 
men, proteine,  gluten,  etc.).  When  the  proteine  substances 
are  burnt  up  in  the  organism  and  transformed  into  urea,  they 
cause  an  oxidation  of  the  sulphur  and  phosphorus,  and  form 
sulphuric  and  phosphoric  acid.  This  explains  the  fact  that  the 
phosphates  and  sulphates  simultaneously  vary  in  quantity  in 
the  urine,  according  to  the  same  laws  as  urea.  We  have 
already  learned  that  a  certain  amount  of  sulphur  (nearly  4 
grms.  in  24  hours)  is  found  in  the  bile  as  tauro-cholic  acid. 

The  pretended  Kiesteine  (more  properly  Kyesteine),  no- 
ticed by  Nauche  and  Golding-Bird,  occurring  in  the  form  of 
a  peculiar  albuminoid  pellicle  floating  on  the  urine  of  a  preg- 
nant woman  does  not  constitute  a  definite  compound.  This 
is  composed  of  an  ammoniaco-magnesia  phosphate  and  of  a 
substance  not  yet  precisely  determined,  called  gramdine  (a 
particular  albuminoid  compound)  by  J.  Starck,  a  caseine  sub- 
stance (the  elements  of  the  commencing  secretion  of  milk 
which  passes  by  reabsorption  into  the  blood  and  thence  into 
the  urine)  by  G.  Bird,  mucus  and  a  proteine  substance  by 
Lehmann,  infusoria  and  vibriones  by  Becharap,  etc. 

There  is  nothing  precisely  known  of  the  influence  of  the 
nervous  system  upon  the  urinary  secretion.  From  what  pre- 
cedes it  is  probable  that  this  influence  is  reduced  to  a  vaso- 
motor action,  which  modifies  the  afflux  and  presence  of  the 
blood  in  the  capillaries  of  the  glomeruli  and  renal  tissue. 

M.  Peyrani  has  sought,  by  means  of  numerous  researches 
on  animals,  to  explain  the  part  played  by  the  great  sympa- 
thetic on  the  urinary  secretion.  He  determined  the  amount  of 
urine  and  urea  first  secreted  during  the  six  hours  preceding 
experimentation,  then  the  six  hours  during  the  galvanic  irri- 
tation of  the  sympathetic,  and  again  during  the  six  hours 
succeeding  the  section  of  the  sympathetic;  and  observed 
that  this  quantity  was  greatest  in  those  cases  where  the 
sympathetic  had  been  cut  (a  section  of  the  cervical  portion 
of  tlie  sympathetic  was  made),  while  galvanization  of  the 
distal  end  of  the  divided  sympathetic  brought  the  quantity 


472  URO-GENITAL  SYSTEM. 

of  urine  and  urea  much  below  the  standard  of  health.  Vul- 
pian  determined  more  precisely  the  modification  of  the  uri- 
nary secretion  by  the  sympathetic  branches ;  his  experiments 
were  made  on  the  splanchnic  nerves.  As  soon  as  either  of 
the  splanchnic  nerves  was  cut,  the  corresponding  kidney  was 
injected,  reddened,  and  increased  in  size ;  the  vein  distended, 
and  the  blood  assumed  an  arterial  brightness;  finally,  the 
urine  secreted  contained  a  much  greater  amount  of  albu- 
men.^ 

C  Excretion  of  urine. 

The  pressure  which  causes  a  filtration  of  urine  pushes  it 
along  through  the  uriniferous  tubes,  and  produces  a  sort  of 
vis  a  tergo^  which  sends  the  liquid  as  far  as  the  summit  of 
the  pyramids  {papillce  renales^  i)a]ullae  of  the  kidney), 
whence  it  flows  out  of  numerous  little  pits,  the  papillary 
orifices^  into  the  calyces  of  the  pelvis;  this  same  force, 
vis  a  tergo^  is  continually  exerted  through  the  course  of  the 
ureters  as  far  as  the  bladder,  for  it  is  hardly  probable  that  the 
contraction  of  their  muscular  walls  is  called  in  play  to  assist 
by  a  series  of  waves  the  propulsion  of  the  urine ;  in  fact,  in 
cases  of  extroversion  of  the  bladder  in  which  the  ureters 
open  in  front  of  the  lower  portion  of  the  abdomen,  as  it  were, 
in  open  sight,  the  urine  may  be  seen  flowing  drop  by  drop 
through  these  orifices  only  as  it  is  produced,  and  in  no  wise 
is  propelled  by  jerks  as  would  be  the  consequence  of  nniscu- 
lar  contractions.  The  ureters  open  into  the  bladder  by 
traversing  in  an  oblique  direction  the  walls  of  this  reservoir ; 
when  the  bladder  is  very  much  distended  the  pressure  on 
these  orifices  must  be  quite  considerable,  and  the  delivery  of 
a  fresh  amount  of  liquid  be  greatly  impeded.  At  such  times 
the  contractility  of  the  ureters  will  assist  by  propelling  the 
urine  with  a  peristaltic  movement,  which  will  afford  sufficient 
force  to  overcome  the  resistance  to  the  passage  of  urine 
along  the  vesical  walls. 

The  bladder  is  a  resei*voir  resulting  from  the  dilatation  of 
the  urachus  or  allantoid pedicle  of  the  fa3tus.  Its  interior  is 
lined  by  an  epithelium,  outside  of  which  are  more  or  less 
regular  muscular  layers. 

The  vesical  epithelium  is  of  the  pavement  or  stratified 
form,  but  its  superficial  cellular  elements  are  remarkable  for 
their  irregularity  and  oddity  of  shape  (Fig.  128).     From  the 

■1  Vulpian,  "  Societe  de  Biologie."    Mai,  1873. 


URINARY  SYSTEM. 


473 


physiological  point  of  view  this  epithelium  is  remarkable  for 
its  impermeability;  it  abso- 
lutely opposes  the  transmis- 
sion of  liquids.  A  solution 
of  belladonna  may  be  kept 
in  a  perfectly  healthy  bladder 
for  a  long,  time,  without  risk 
of  poisoning  from  atropine ; 
so,  also,  may  solutions  of 
opium,  without  danger  of 
opium  poisoning.  But  if  the 
epithelium  is  diseased,  ab- 
sorption immediately  occurs ;  _,  ^„„  ^  .^,  „  ,  ^^  vi  n  * 
I  11  Fig.  128.— Epithelium  of  the  bladder.* 

and,  as   an   example,   when 

dilute  alcohol  is  injected  into  the  bladder  in  which  there  ex- 
ists catarrhal  inflammation,  symptoms  of  alcoholic  intoxica- 
tion are  manifested.  The  vesical  epithelium  even  for  some 
hours  after  death  preserves  its  vitality  and  consequently  its 
impermeability.  If  ferro-cyanide  of  potassium  be  injected 
through  a  tube,  thus  preventing  contact  with  the  urethral 
mucous  surface,  into  the  bladder  of  an  animal  which  has  just 
been  killed,  then  the  bladder  be  exposed  and  a  ferric  salt 
placed  upon  the  outside  of  its  w^alls,  no  Prussian  blue  will  be 
seen.  This  experiment  shows  that  the  two  salts,  which  in 
contact  would  produce  Prussian  blue,  are  separated  by  an 
impassable  barrier,  viz.,  the  epithelium.  Yet  if  by  means  of 
a  wire  the  epithelial  coat  on  the  inside  of  the  bladder  be 
scratched  or  destroyed  at  this  point,  Prussian  blue  will  be 
immediately  formed.  This  opposition,  then,  to  the  passage 
of  liquids  results  solely  from  the  presence  of  the  epithelium.^ 
The   muscular  fibres   of   the   bladder  are    smooth,   and 


1  For  a  further  verification  and  elucidation  of  the  above  statement 
the  reader  is  referred  to  Ch.  Robin,  "  Lemons  sur  les  Humeurs." 
1867,  p.  22.  Also,  see  J.  J.  C.  Susini,  "  De  I'lmpermeabilite  de 
I'Epithelium  Vesical."  These  de  Strasbourg,  18 j7,  No.  30.  The 
epithelium  of  the  urethra  being  much  less  resisting,  and  possessing 
a  different  character  (columnar  and  pavement  cells),  permits  ab- 
sorption.    (See  Ailing,  These  de  Paris,  1871.) 

*  a,  Voluminous  cell,  with  the  edges  notched ;  smaller  spindle-shaped  cells 
are  attached  to  these  edges,  b,  Analogous  cells ;  the  most  voluminous  has  two 
nuclei,  c,  A  still  larger  cell,  irregularly  quadrilateral,  with  four  nuclei,  c?, 
Analogous  cell,  as  seen  in  front,  with  two  nuclei,  and  pitted,  the  pits  correspond- 
ing to  the  notches  of  the  edges,  above.  (Virchow,  "Path.  Cell.,"  and  "Archiv. 
fur  Pathol.  Anat."     Vol.  ill.  .Tab.  1,  Fig.  8.) 


474 


URO-GENITAL  SYSTEM. 


consequently  have  slow  and  lazy  contractions;  but  they  nro, 
moreover,  very  elastic,  and  allow  the  bladder  to  dilate  readily, 
as  well  as  the  urine  to  accumulate  in  large  quantity.  When 
this  dilatation  is  pushed  to  its  extreme  extent,  it  becomes  a 
cause  of  irritation  to  the  muscular  fibre,  which  will  then  con- 
tract, and  the  bladder  expel  its  contents.  We  shall  soon  see 
that  this  reaction  occasions  a  desire  to  urinate.  When  there 
is  inflammation  of  the  bladder,  its  muscular  walls  are  less 
elastic  (seo.  Physiology  of  the  Muscle)^  and  these  more 
quickly  react  upon  the  contents  of  the  reservoir,  and  occasion 
in  such  cases  frequent  desire  for  micturition. 

The  important  question  now  presents  itself  as  to  how  the 
urine,  during  the  quiescence  of  the  bladder,  is  retained  in 
this  reservoir  and  does  not  escape  through  the  orifice  in  the 
neck  of  the  bladder.  We  all  know  that  this  is  closed  by  a 
contraction  of  the  vesical  sphincter  which  surrounds  the 
opening;  but  these  muscular  fibres  are  not  very  pronounced, 
nor  can  a  muscle  be  kept  in  a  continual  state  of  contraction. 
The  neck  of  the  bladder  is  closed,  because  this  is  its  natural 
form,  like  that  of  other  and  similar  circular  muscles ;  these 
obliterate  the  orifice  which  they  circumscribe,  when  they  are 
in  a  state  of  repose,  and  this  is  simply  due  to  their  elasticity. 
But  so  soon  as  some  cause  opposes 
this  sphincter,  it  becomes  powerless 
to  prevent  the  passage,  which  the 
urine  overcomes  and  rushes  through. 
With  women  this  orifice  is  difter- 
ently  arranged,  and  on  a  slight  effort, 
Vis  or  burst  of  laughter,  several  drops 
of  urine  may  gush  out.  Certain 
arrangements  and  especial  positions 
of  the  bladder,  especially  in  man, 
are  of  such  a  nature  that  there  ex- 
ists no  real  orifice  while  the  bladder 
is  in  a  state  of  repose. 

First,  the  axis  of  the  bladder 
(Fig.  129)  is  by  no  means  vertical, 
but  almost  horizontal  (this  organ  rests  upon  the  symphysis 
pubis,  which  has  almost  a  horizontal  position)  ;  the  excretory 

♦  S,  Symphisis  pubis,  ps^  Plexus  of  Santorini.  V,  Bladder.  0,  Remains 
of  the  urachus.  P/>,  Prostrate  gland.  U/?,  Prostatic  utricle.  C(/,  Deferent 
canal.  Vs,  Vesiculoe  seminales,  whose  neck  joins  with  the  deferent  canal  to  form 
the  excretory  duct,  which  may  be  seen  going  behind  the  prostatic  utricle. 
W,  The  so-called  Wilson's  muscle  (pubo-urethral  band).  Gp,  Cowper's  gland. 
1],  Bulb  of  the  irethra. 


Fig.  129.  —  Bladder  and  organs 
of  micturition.* 


URINARY  SYSTEM.  475 

canal,  urethra,  has  first  a  position  vertically  downwards,  then 
it  turns  and  curves  forwards ;  thus,  this  canal  is  liable  to  be 
compressed  by  the  enormous  distention  of  the  bladder. 

Again,  the  prostate  gland  (Pp,  Fig.  129)  is  a  hard  unyield- 
ing organ,  being  composed  of  glands,  fibrous  tissue,  and 
muscular  elements;  this  urethral  opening  penetrates  and  is 
encircled  by  this  prostate  gland  in  such  way  as  to  have  its 
walls  closed  by  contact.  This  forms  the  principal  cause  in 
man  of  the  retention  of  urine  during  the  inaction  of  the 
bladder.  Should  the  prostate  gland  become  hypertrophied, 
a  still  greater  obstacle  (too  much  so  in  old  men)  is  made  to 
the  passage  of  urine,  and  becomes  the  cause  of  a  pathological 
retention. 

Finally,  the  flattening  of  the  urethral  canal  and  its  closure 
by  contact  are  influenced  by  the  arrangement  of  the  perineal 
fasciaB,  the  fibres  of  which  press  upon  the  sides  of  the  ure- 
thral canal  in  their  course  from  the  ischium  to  the  pubis ;  and 
a  certain  muscular  and  expulsive  efibrt  is  requu-ed  to  over- 
come this  constraint,  and  dilate  the  orifice. 

It  is  not  surprising  in  view  of  this  explanation  that  the 
urine  is  allowed  to  accumulate  in  this  muscular,  dilatable,  and 
elastic  reservoir,  and  that  no  physiological  act  or  contraction 
is  required  to  prevent  the  exit  of  the  urine ;  these  conditions 
are  simply  mechanical  and  continue  after  death,  since  urine 
is  often  found  in  the  bladder  of  the  dead  body. 

When  the  walls  of  the  bladder  become  too  much  distended 
by  the  presence  of  urine,  we  have  said  that  a  compression  of 
the  contents  is  produced  by  contraction  of  the  smooth  mus- 
cular fibres;  this  overcomes  the  elasticity  of  the  neck  of  the 
bladder  and  of  the  prostate,  and  the  urine  passes  into  the 
bulbous  portion  of  the  urethra  :  here  it  comes  in  contact  with 
a  very  sensitive  mucous  surface,  the  prostatic  mucous  m'ein- 
hrane,  which  presides  over  a  large  number  of  reflex  phenom- 
ena. It  is  owing  to  this  contact  of  the  urine  with  the  mucous 
surface  that  we  experience  that  peculiar  sensation  of  a  neces- 
sity or  desire  for  micturition^  and  which  we  refer,  in  common 
with  almost  all  other  sensations  of  this  region,  to  the  fossa 
navicularis.  If  we  pay  no  attention  to  this  desire,  a  reflex 
irritation  is  produced,  which  is  followed  by  the  contraction 
of  the  constrictor  urethrae,  or  urethral  sphincter ;  the  urine 
can  then  go  no  farther,  and  is  even  obliged  to  retrograde,  on 
account  of  the  contraction  of  the  muscles  on  the  anterior  por- 
tion of  the  prostate,  and  so  re-enters  the  bladder  whose  con- 
tractions have  ceased. 


476  URO-GENITAL  SYSTLJf. 

These  co-ordinated  contractions,  wliicli  occasion  micturition, 
are  made  nnder  the  influence  of  the  spinal  cord,  and  particu- 
larly its  lumbar  portion.  Budge  has  sought  to  fix  the  precise 
seat  of  this  centre,  and  by  experiments  has  placed  the  centre 
of  innervation  of  the  bladder  in  the  fourth  lumbar  vertebra 
(in  dogs  and  rabbits).  Kupresson  localizes  this  centre  be- 
tween the  fifth  and  sixth  lumbar  vertebrae. 

Sensibility  of  the  prostatic  mucous  surface  is  very  impor- 
tant, since  this  is  the  point  of  origin  for  the  essential  reflex 
action ;  loss  of  this  sensibility  is  the  cause  of  that  form  of  in- 
continence of  urine  called  enuresis,  or  nocturnal  incontinence ; 
this  involuntary  voiding  of  urine,  as  in  similar  cases  of  invol- 
untary emission  of  feces,  is  explained  by  the  lack  qfsensibilUi/ 
of  the  mucous  surfaces  to  the  contact  of  excrementitial  pro- 
ducts, and  in  this  particular  case,  the  absence  of  a  premon- 
itory sensation  of  the  desire  to  urinate. 

Some  moments  after  the  continued  distention  of  the  vesical 
resei-voir,  it  reacts  anew,  and  the  urine  proceeds  to  the  pros- 
tatic portion  of  the  urethra,  where  it  stimulates  anew  the 
same  reflex  action,  and  so  on.  This  explains  the  intermittent 
form  of  the  desire  for  micturition.  If  these  phenomena  are 
often  repeated,  the  reflex  contraction  of  the  urethral  sphincter 
gradually  loses  its  energy,  and  the  urine  tends  to  pass  out 
through  the  urethral  canal;  hence  the  distress  occasioned  by 
resisting  the  desire  to  urinate.  Thus  it  is  seen  that  every 
time  a  true  active  resistance  is  ofiered  to  the  passage  of  urine, 
this  opposition  is  made,  not  by  the  sphincter  of  the  bladder, 
but  by  the  sphincter  of  the  urethra,  the  constrictor  urethroB 
muscle,  which  is  the  only  one  of  these  muscles  which  is 
striated  or  voluntary.^ 

If  a  sound  be  introduced  into  the  urethra,  as  soon  as  its  tip 
touches  the  mucous  membrane  of  the  prostatic  portion,  it  will 
occasion  a  sensation  similar  to  the  desire  to  urinate ;  we  refer 
this  sensation  to  the  other  extremity  of  the  urethra,  simply 
bciiause  it  is  one  of  those  associated  sensations,  examples  of 
which  we  have  already  cited.  (See  General  Sensibility  and 
/Sensations,  pp.  79  and  388.) 

When  we  yield  to  the  desire,  in  spite  of  the  absence  of 
any  obstacle  on  the  part  of  the  sphincter  or  constrictor 
urethrse,  we  cannot  completely  evacuate  the  contents  of  the 
bladder  by  the  simple  contraction  of  its  walls.     We  must 

*  See  Carayon,  "  De  la  IViiction  dans  ses  Rapports  avec  la  Phy- 
fiiologie  et  la  rathologie."     These  de  Strasbourg,  1865,  No.  814. 


GENITAL  SYSTEM.  477 

call  in  to  our  assistance  the  abdominal  muscles,  by  means  of 
•which  the  abdominal  viscera  will  press  upon  the  bladder  and 
increase  the  expulsive  efforts  of  its  walls.  We  close  the 
glottis  at  the  very  beginning  of  micturition,  and  then  the 
vesical  contraction  is  sufficient  for  the 

expulsion  of  urine.    But  towards  the  end     ^ JL^^ 

of  micturition,  in  order  to  expel  the  last    f         ^--^^\ 

drops,  a  renewed  effort  is  necessary :  the    I      /'       j     N\ 
lowest  portion  of  the  bladder  being  fixed    \     j      y'"'"^^^^  \  \ 
and  concave,  we  could  not  evacuate  it   yvv   •     4-L  \:/ 
completely,  unless,  by   the   aid   of  the     y^^S/  3  S.'-^ , 
abdominal    muscle,    we    compress    the    gP^^^g;;--!-^'^^^ 
upper  against  the  lower  portion  of  the        xJ^^^^^Bl 
bladder  in  such  a  way  as  to  completely         ^^^w^r"^ 

obliterate  the  cavity  (Fig.  130)  ;  in  man,  ^" w^  . 

then,    the    bladder     when    completely 

emptied  (not  so,  however,  with  all  ani-    Fig.  loi.- Diagram  of 

mals)  resembles  a  cup,  and  m  this  form 

it  is  seen  in  the  dead  body  when  this  reservoir  is  completely 

empty. 

As  soon  as  the  bladder  has  been  emptied,  the  walls  of  the 
urethra  are  brought  in  contact  and  expel  its  contents;  but 
when  this  canal  is  diseased  and  long-seated  inflammation  has 
destroyed  the  elasticity  of  the  bladder,  it  is  not  thoroughly 
em)ilied,and  the  urine  remaining  in  contact  with  the  mucous 
surface,  contributes  to  keep  up  the  pathological  condition. 


n.    GENITAL   SYSTEM. 
I.  Male  Organs  of  Generation. 

The  male  organs  of  generation  are  composed  of  a  gland 
(testicle)  and  a  series  of  excretory  ducts. 

1.  The  male  gland.,  the  testicle^  is  the  offshoot  from  an 
organ  which  is  developed  on  the  inner  edge  of  the  Wolffian 
body  (see  above) ;  until  the  close  of  the  second  month  this 
body  presents  no  characteristic  feature  that  would  lead  us  to 
know  whether  it  were  a  testicle  or  an  ovary ;  but  towards 

*  This  diagram  shows  how  the  bladder  is  completely  emptied. 

1,  Outline  of  the  bladder  when  distended  by  a  liquid.  2,  3,  4,  5,  Represents 
the  outline  of  the  bladder  when  reduced  by  different  intensities  of  its  contrac- 
tions. 6,  Represents  the  outline  when  the  abdominal  muscles  have  adjusted  the 
upper  to  the  lower  concave  portion.  The  arrow  indicates  the  direction  iu  which 
the  compression  is  made. 


478  URO-GENITAL  SYSTEM. 

tlie  third  month,  if  it  is  to  be  a  testicle,  the  canaliculi  of  the 
Wolffian  body  penetrate  into  its  substance,  there  multiply,  and 
become  the  seminiferous  tubuli.  At  the  same  time  the  other 
portion  of  this  body  is  atrophied,  and  the  remaining  por- 
tions with  its  excretory  canal  constitute,  the  former  certain 
rudimentary  organs  {non-pediculated  hydatid  of  Morgagni, 
corpus  innominatum  of  Giraldes),  whilst  from  the  latter  are 
formed :  the  excretory  ducts  of  the  testicle,  caput  or  head 
and  body  of  the  epididymis^  vas  deferens,  with  numerous 
more  highly  convoluted  tubes,  which  are  the  remains  of  the 
a[)pendages  of  the  Wolffian  body;  of  these  the  most  note- 
worthy and  constant  becomes  the  vas  aberrans. 

In  this  way  the  internal  genital  organs  of  man  essentially 
spring  from  the  Wolffian  body ;  and  form  the  testicle,  vesicula9 
seminales,  and,  finally,  the  ejaculatory  canals;  in  brief,  form 
all  the  organs  that  are  comprised  between  the  seminal  gland 
and  the  genito-urinary  sinus  (prostatic  portion  of  the  urethra). 
The  Miillerian  duct  (see  p.  518)  is  completely  atrophied  in 
man ;  its  only  remaining  trace  is  found  in  the  two  extremi- 
ties that  form  the  pediculated  hydatid  of  Morgagni,  and  the 
central  portion,  which  unites  with  that  of  the  opposite  side  to 
form  the  utriculus  prostaticus.  We  shall  see  that  the  Miil- 
lerian ducts  represent  the  whole  of  the  genital  organs  in 
woman,  and  especially  form  the  womb,  by  the  fusion  of  the 
two  inferior  portions  of  the  duct  on  each  side,  in  the  same 
way  that  the  prostatic  utricle  is  formed  in  man :  the  utricu- 
lus prostaticus  and  the  uterus  are  homologous  organs. 

A.  Testicle  and  its  excretory  canals.  —  Formation  of  the 
spermatic  fluid. 

a.  The  seminiferous  tubes  of  the  testicle  are  sinuous  tubes, 
tortuous  like  the  tubes  of  Ferrein  in  the  cortical  substance 
of  the  kidney,  and  terminate  at  the  posterior  edge  of  the  tes- 
ticle in  what  is  called  the  corpus  Highmori  (Fig.  131,  Qh), 
an  eminence  of  compact  fibrous  tissue,  wherein  the  seminif- 
erous tubes  cross  (rete  testis)  to  go  to  the  excretory  canals 
that  form  the  epididymis. 

The  seminiferous  tubes  are  quite  numerous :  500  or  1000 
have  been  counted  in  each  testicle ;  they  appear  in  the  form 
of  tubes  with  thin  walls,  almost  entirely  filled  with  polyhedral 
epitheUum.  This  epithelium  produces  the  spermatic  fluid, 
whose  secretion  is  temporary  and  not  continuous.  The  testi- 
cle is  inactive  in  childhood  and  old  age.  At  the  period  of 
puberty,  among  the   epithelial  cells  of  these   tubes,   quite 


GENITAL  SYSTEM. 


479 


voluminous  seminiferous  cells  may  be  distinguishecl,  mother 
cells,  which  result  from  the  development  of  the  primitive 
globules ;  these  cells  may  be  compared  to  the  ovum  of  the 
woman :  like  the  ovum  these  former  cells  are  set  free,  have 


Fig.  131.  —  Genital  system  in  man* 


Fig.  132.  — Spermatozoids.* 


an  independent  existence,  and  move  about  in  a  liquid  caused 
by  the  moulting  of  neighboring  globules ;  they  are  gradu- 
ally chased  through  the  epididymis  and  vas  deferens.  Dur- 
ing their  progress  these  cells,  called  masculine  ova  {ovule 
m^asculin,  Ch.  Robin ),^  undergo  an  active  endogenous 
segmentation,  and  give  birth  to  new  globular  forms 
which  were  contained  in  them:  these  are  the  spermato- 
zoids,  which  are   first   seen   as  filaments  rolled  up  in  the 


^  See   C.   N.    Dem^triesco, 
These  de  Paris,  1870. 


Etude  sur  les   Ovules  Males." 


*  T,  Testicle.  C^,  Corpus  Highmori,  with  the  rete  testis.  E,  Caput  Epidi- 
dymis, fonned  by  the  union  of  the  seminiferous  cones.  E',  Tail,  caudn,  or 
globus  of  the  epiclidymis.  Va,  Vas  aberrans.  Cd,  Vas  deferens.  Ys,  Vesicula 
seminalis.  P,  Prostate,  with  ejaculatory  canal ;  prostatic  utriculus  and  vera 
montanum  during  erection  (1).  2,  So-called  muscle  of  Wilson,  in  a  state  of 
contraction,  obliterating  the  canal  (at  this  moment  the  spermatic  fluid  can  only 
accumulate  in  the  prostatic  portion  of  the  urethra  between  the  points  1  and  2, 
whence  it  is  propelled  by  the  contractions  of  the  preceding  canals  from  E  to 
VS).    G/),  Cowper's  gland.    V,  Bladder. 

*  a,  6,  Spermatozoids,  taken  from  inside  of  the  testicle,  c,  From  the  vaa 
deferens,    a,  From  the  vesiculie  seminales. 


480  URO-GENITAL  SYSTEM. 

globules  of  the  mother  cells,  but  which  are  set  free  when  the 
latter  are  broken.  These  spermatozoids  afterwards  show  a 
slight  pear-shaped  and  flattened  swelling  {head)^  and  a  fili- 
form appendage  (or  tail)^  terminating  in  a  fine  point  (Fig. 
132).  Generally  only  the  mother  cells  are  found  in  the  tubes 
of  the  testicle. 

In  those  animals  who  enjoy  the  sexual  functions  only  at 
certain  periods  of  the  year,  the  testicular  secretion  occurs 
only  at  those  periods :  they  begin  in  man  only  at  the  age  of 
puberty.  Spermatozoids  are  never  found  in  the  spermatic 
fluid  before  the  age  of  16  or  17  years.  They  likewise  are 
liable  to  disappear  in  old  age.  According  to  Dr.  Girault,  in 
man  after  the  age  of  55  years  the  head  of  the  spermatozoids 
is  broader  and  the  tail  is  shorter;  then  comes  a  time  when 
these  species  of  tadpoles  {tetards)  have  almost  no  tail :  the 
head  has  absorbed  almost  the  whole  of  this  tail ;  a  few  move- 
ments may  exist,  but  progression  has  become  impossible :  a 
few  scattered  ones  in  whom  the  tail  remains  have  the  power 
to  go  forward. 

b.  The  spermatic  fluid  is  perfected,  or  in  other  words,  the 
gpermatozoids  are  set  free,  only  in  the  epididymis  (Fig.  131, 
E)  and  in  the  canals  (E',  Cd)  :  they  then  seem  to  be  ani- 
mated with  very  active  movements  of  transportation,  but,  in 
reality,  only  represent  the  movements  of  vibratile  cilia  (see 
p.  189).  Sometimes  the  head  or  the  neck  (union  of  the  head 
with  the  tail)  of  the  spermatozoid  is  encircled  by  a  sort  of 
collar  or  frill,  w^hich  is  the  remains  of  the  nucleus  in  which 
the  spermatozoid  was  developed.  Their  movements  become 
more  noticeable  in  that  spermatic  fluid  which  is  formed  by 
the  product  of  all  the  various  glands,  and  as  found  in  the  ejacu- 
latory  ducts ;  the  head  moves  to  and  fro  by  means  of  the 
impulsion  received  from  the  movements  of  the  tail.  No  sper- 
matic fluid  is  capable  of  eflTecting  fecundation  which  has  not 
these  vibratile  and  moving  filaments.  This  sperm,  which 
has  a  tenacious  whitish  appearance,  and  a  peculiar  odor,  con- 
tains an  albuminoid  substance  called  spermatine :  this  latter 
substance  is  not  coagulated  by  heat,  contains  various  salts 
(alkaline,  chlorides,  phosphates,  sulphates),  and,  as  physical 
or  morphological  elements,  it  also  contains  a  large  number 
of  granulations,  in  addition  to  the  spermatozoids,  and  likewise 
certain  crystals  which  are  analogous  to  the  ammonio-magnesia 
crystals  of  the  urine,  but  now  considered  to  be  altered  and 
crystallized  albuminates. 

The  sperm  progresses  through  the  epididymis  (Fig.  131,  E^ 


GENITAL  SYSTEM.  481 

and  the  vas  deferens  (E',  Cd)  by  means  of  the  vis  a  tergo 
and  by  contractions  of  the  muscular  fibres  in  these  canals. 
Venereal  excitations  singularly  hasten  its  production  and 
secretion ;  but  when  these  excitations  are  repeated  at  too 
short  intervals,  the  spermatic  fluid  has  no  time  to  be 
thoroughly  elaborated,  and  hence  the  spermatozoids  are  often 
fjund  in  the  ejaculated  secretion  still  enveloped  in  their 
mother  cells. 

In  its  course  from  the  testicle  to  the  prostatic  region,  the 
sperm  may  turn  aside  into  the  vesiculm  seminales  (Fig.  181, 
V  s),  which  might  be  looked  upon  as  a  diverticulum  of  the 
vas  deferens  (spermatic  duct)  analogous  to  the  vas  aberrans 
(Fig.  131,  Va),  which  are  derived  from  the  lateral  cceca 
of  the  Wolfiian  body;  but  the  function  of  a  spermatic  reser- 
voir assigned  to  the  seminal  vesicles  has  never  been  perfectly 
demonstrated :  most  often  there  has  only  been  found  in  this 
diverticulum  a  yellowish  mucus,  which  apparently,  in  the 
8ame  way  as  the  prostate  and  Cowper's  glands,  gives  to  the 
sperm  a  more  fluid  character.  The  red  globules  of  the  blood 
are  frequently  found  in  the  product  of  the  seminal  vesicles, 
especially  when  there  has  been  no  coition  for  a  long  time 
(Ch.  Robin),  but  their  presence  need  cause  no  alarm.  The 
concretions  which  are  found  in  these  products  are  proved 
by  their  chemical  properties  to  be  formed  of  the  nitro- 
genous concrete  mucus.  The  seminal  vesicles  are  not  found 
in  a  large  number  of  the  lower  animals,  especially  not  the 
dog. 

By  peristaltic  movements  of  the  efferent  system,  the  sper- 
matic fluid  is  thrown  along  the  ejaculatory  ducts  into  the 
prostatic  portion  of  the  urethra ;  these  ducts  lead  from  the 
seminal  vesicles  and  the  termination  of  the  vas  deferens 
towards  the  posterior  wall  of  the  urethra  (Fig.  131,  p.  479). 
Then  they  pass  through  the  posterior  half  of  the  prostate 
gland.  In  spite  of  the  name  ejaculatory^  these  ducts  take  no 
active  part  in  this  mechanical  phenomenon  :  their  thin  walls, 
which  are  nearly  devoid  of  muscular  elements,  would  not 
allow  of  any  active  contraction.  They  serve  only  to  conduct 
the  sperm  to  the  prostatic  region,  at  which  latter  place  its 
contact  with  the  sensitive  mucous  surface  excites  a  peculiar 
reflex  action,  the  ejacidation^  whose  mechanism  it  is  ex- 
tremely difficult  to  study,  but  which  is  destined  to  project 
the  male  fecundating  fluid  into  the  female  organs  of  gener- 
ation.    We  shall  first  proceed  to  the  consideration  of  a  phe- 

81 


482  URO-GENITAL  APPARATUS. 

nomenon  which  precedes  and  renders  this  act  more  efficacious, 
viz.  erection. 

A.  Erection. 

The  apparatus  of  erection  is  composed  of  the  penis,  its 
cavernous  body  and  its  spongy  body  (also  the  bulb  and  glans). 

The  object  of  erection  consists  in  phicing  the  urethral 
canal  in  the  most  favorable  posture  for  the  easy  flow  of  the 
spermatic  fluid,  and  for  its  transportation  into  the  female 
organs  of  generation. 

Erection  is  caused  by  a  reflex  action,  whose  point  of  origin 
is  in  the  brain  (imagination),  and  in  most  of  the  organs  of  the 
senses  as  well  as  in  the  sensitive  surfaces ;  but  the  excitation 
of  the  mucous  surface  of  the  glans  penis  carries  this  reflex 
action  to  its  highest  degree.  Indeed,  the  glans  is  furnished 
with  numerous  nervous  papillae  which  gives  to  it  a  special 
sensation,  called  genital ;  the  excitation  of  this  sensibility  is 
the  point  of  origin  for  that  chain  of  acts  which  constitutes 
coitus  (erection,  abundant  secretion  of  sperm,  excretion, 
ejaculation),  just  as  the  excitation  of  the  fauces  is  the  signal 
for  the  series  of  acts  of  deglutition.  The  dorsal  nerve  of  the 
penis  is  the  centripetal  path  for  these  reflex  phenomena, 
which  become  impossible  after  section  of  this  nerve,  as  at- 
tested by  many  repeated  experiments  on  horses. 

The  question  of  the  mechanism  of  erection  is  very  com- 
plicated, and  upon  it  there  is  little  agreement :  it  has  been 
demonstrated  that  this  phenomenon  essentially  consists  in 
an  accumulation  of  blood  in  the  texture  of  the  cavernous 
and  spongy  portion  of  the  erectile  apparatus,  but  the  embar- 
rassment lies  in  the  explanation  as  to  how  this  blood  is  re- 
tained, and  at  so  high  a  tension.  Yet  a  few  circumstances 
can  clear  up  this  study ;  thus  it  is  admitted  that  an  erection 
of  the  cavernous  body  is  often  independent  of  that  of  the 
spongy  portion  of  the  urethra,  and  can  result  without  genital 
excitement,  by  a  simple  and  mechanical  opposition  to  the 
return  of  the  venous  blood ;  to  this  kind  of  erection  belongs 
that  produced  when  the  bladder  is  distended  with  its  fluid 
contents;  this  is  followed  by  a  compression  of  those  venous 
plexus  which  are  formed  by  an  expansion  of  the  dorsal  vein 
of  the  penis  (prostatic  or  plexus  of  Santorini,  placed  between 
the  bladder  and  pubis  j05.  Fig.  129,  p.  474).  It  is,  then,  prob- 
able that  when  the  erection  is  really  active  it  produces  upon 
all  the  veins  coming  from  the  erectile  parts  a  similar  constric- 


GENITAL  SYSTEM.  483 

tion,  either  by  contraction  of  the  walls  of  the  veins,  or  of  the 
numerous  layers  of  smooth  muscles  through  which  these  veins 
pass  before  entering  the  pelvis  (the  middle  layer  of  the  peri- 
neal fascia  are  almost  entirely  composed  of  smooth  muscular 
fibres) ;  this  would  tend  to  arrest  the  blood  in  the  texture 
of  the  spongy  tissues,  and  so  produce  a  pressure  equal  to  that 
of  the  arterial  blood. 

In  this  way  erection  depends  upon  a  reflex  contraction 
which  arrests  the  progress  of  blood  in  the  veins ;  and,  in 
fact,  a  pathological  erection  observed  in  dead  subjects  is 
associated  with  clots  which  fill  the  veins  of  the  erectile  tissue 
and  extend  to  the  veins  of  the  pelvis ;  this  would  seem  to 
prove  that  the  compression  occurs  in  the  pelvic  cavity. 

Perhaps,  also,  vaso-motor  paralysis  (see  p.  170,  Circulation) 
has  a  certain  influence  upon  the  mechanism  of  erection,  by 
allowing  the  erectile  tissues  to  be  distended  with  the  afflux 
of  blood ;  yet  it  is  evident  that  if  the  path  for  the  return  of 
the  venous  blood  should  remain  freely  open,  the  vaso-motor 
paralysis  would  not  be  sufiicient  for  the  production  of  a  true 
erection,  and  would  only  induce  a  more  or  less  pronounced 
turgescence. 

Professor  Rouget^  has  established  that  in  all  cases  there 
exists  a  dilatation  of  the  small  arteries ;  this  same  efiect  is 
observed  in  the  hyperasmia  of  the  ovary  and  the  uterine 
mucous  surface  at  the  commencement  of  the  act  of  menstru- 
ation, and  is  due,  in  his  opinion,  to  the  same  causes  as  blush- 
ing and  the  reddening  of  the  crest  or  comb  of  the  male  fowl 
called  the  cock.  Finally,  direct  observation  of  the  com- 
mencement of  the  erection  of  the  organs  of  copulation,  and 
the  experiments  of  Eckhard  on  the  paralysis  of  the  small 
arteries  of  the  cavernous  and  bulbous  portions  of  the  urethra 
after  irritation  of  the  nervi  erigentes  ;  both  of  these  phenom- 
ena prove  that  paralysis  and  vascular  dilatation  are  the  initial 
phenomenon  of  all,  even  the  most  complicated  kind  of  erec- 
tion.^ 

But   this   phenomenon,   though  sufficient    to   prove   the 

^  Ch.  Rouget,  "  Recherches  sur  les  Organes  Erectiles  de  la 
Femrae."  ("Journal  de  Physiologie,"  Vol.  I.,  1858.)  "  Des 
Mouvements  Erectiles."     (Ibid.,  18G8.) 

2  Thus  we  can  call  to  mind  in  view  of  erection  all  that  has  been 
said  in  regard  to  the  physiology  of  the  vaso-motor  nerves.  To 
this  class  of  phenomena  belong  the  theory  of  aciive  dUataiion  of 
Schiif ,  and  the  per istaltism  of  tlie  blood-vessels  of  Legros  and  Oni- 
Hius  (see  Vaso-motors,  pp.  173  et  seq.). 


484  URO-GENITAL  APPARATUS. 

simplest  form  of  erection,  or  turgescence^  would  not  suffice  for 
those  more  complicated  forms,  as  the  erection  of  the  bulb, 
ovary,  and  uterus ;  we  must  consider  that  the  smooth  mus- 
cular trabecula3  assist  in  the  compression  of  the  venous 
trunks ;  and  it  is  equally  certain  that  at  the  period  of  men- 
struation this  permanent  contraction  of  the  uterine  muscles, 
and  those  of  the  Fallopian  tube,  coincide  with  the  application 
of  the  tube  to  the  ovary,  and  accomplish  this  phenomenon. 
It  is  also  true  that  the  muscular  trabeculaB  of  the  spongy  and 
cavernous  tissue  of  the  penis  contract,  after  the  dilatation  of 
the  small  arteries.  When  this  latter  contraction  does  not 
occur,  as  in  the  dead  subject,  the  size  of  the  penis  may  be 
made  enormous,  and  yet  its  rigidity  be  relatively  incom- 
plete. 

Finally,  in  the  erection  of  the  organs  of  copulation  of  both 
sexes,  the  action  of  the  extrinsic  muscles  is  brought  in  play 
in  order  to  complete  its  development;  and  in  fact  we  know 
that  an  injection  by  the  most  forcible  pressure  will  not  pro- 
duce a  true  erection  unless  preceded  by  ligation  or  compres- 
sion of  the  large  veins  in  the  pelvis. 

The  centrifugal  nerves  which  share  in  the  function  of  erec- 
tion have  been  classified  in  two  groups,  whose  action  is  dis- 
tinct and  antagonistic  (Rouge t). 

1.  The  cavernous  and  spongy  nerves  (branches  of  the  large 
cavernous  nerve  given  off  from  the  prostatic  plexus)  are  sup- 
plied from  the  grand  sympathetic,  and  belong  to  that  class  of 
nerves  which  are  provided  with  ganglionic  corpuscles,  whose 
irritation  results  in  the  paralysis  of  those  arterial  coats  inner- 
vated by  these  nerve  fibres  {nervi  erigentes  ofEckhard). 

2.  Those  nerves  which  go,  without  traversing  the  gangli- 
onic corpuscles,  to  the  muscles  of  the  trabeculse,  and  whose 
irritation  is  followed  by  contraction  of  the  muscles  which 
they  supply  {nerfs  urethro-peniens,  plexus  lateral)  \  so  also 
anirritationof  the  direct  nerves  (and  without  ganglia)  which 
innervate  the  erector  penis,  accelerator  urince,  and  the  in- 
ferior transverse  muscles,  is  followed  by  contraction  of  these 
muscles. 

The  erector  penis  and  accelerator  urince  muscles  may  be 
called,  from  ihQir  fuwciion^,  true  peripheral  hearts ;  their  func- 
tion consists  in  chasing  the  blood  from  the  base  to  the  free 
extremity  of  the  penis.  The  former  of  these  two  muscles 
encircles  the  root  of  the  corpus  cavernosum,  the  latter  the 
bulb  of  the  urethra,  and  by  their  rhythmical  contractions 
cause  the  erection  of  the  penis  from  the  base  to  its  summit. 


I 


GENITAL  SYSTEM.  485 

These  muscles  contract,  in  virtue  of  a  reflex  action  (see 
above),  influenced  by  the  irritation  of  the  glans  penis^  and  at 
each  contraction,  we  might  almost  say  at  each  pulsation,  of 
the  accelerator  wince  muscle,  the  glans  become  more  swollen 
and  sensitive ;  and  its  papillse  being  extended  over  a  larger 
surface  are  more  highly  excited  by  the  continued  friction. 
When  this  sensation  has  reached  its  highest  point,  it  occa- 
sions the  reflex  phenomenon  of  ejaculation, 

C.  Ejaculation, 

Ejaculation  is  the  termination  of  the  venereal  act,  and  its 
accomplishment  is  preceded  by  numerous  accessory  acts. 

In  the  first  place,  by  the  fact  of  erection  the  urethral  canal 
is  dilated  and  open.  This  dilatation  would  naturally  produce 
a  certain  aspiration  or  suction,  and  something  must  fill  the 
canal  which  is  transformed  from  a  flattened  to  a  cylindrical 
shape :  it  has  been  supposed  that  air  is  thus  introduced,  and 
this  hypothesis  would  explain  also  those  cases  of  chancres 
found  in  the  interior  of  the  urethra ;  and  assuming  that  aspira- 
tion during  coitus  has  sucked  into  the  canal  a  virulent  liquid 
from  the  contaminated  woman.  Yet  observation  has  shown 
that  air  does  not  rush  in  to  fill  the  enlarged  cavity,  for  in  that 
case  particles  of  air,  in  the  form  of  bubbles,  would  be  found 
in  the  excreted  spermatic  fluid ;  this  latter  phenomenon  has 
never  been  observed.  Cowper's  glands,  analogous  to  the 
salivary  glands,  which  are  situated  amongst  the  striated  and 
smooth  muscular  fibres  of  the  perineum  (middle  fasciae),  and 
behind  the  enlargement  of  the  bulbous  portion  of  the  urethra 
(Fig.  131,  p.  479),  secrete  a  fluid  which  would  fill  the 
vacuum  in  the  canal ;  the  excretory  duct  from  these  glands 
opens  into  the  urethra  at  the  union  of  its  bulbous  and  spongy 
portions.  The  product  of  these  glands  thus  would  dilute 
the  spermatic  fluid,  which  primarily  is  quite  thick.  If  a  de- 
cided erection  is  not  followed  by  the  ejaculation  of  the  sperm  ; 
at  the  cessation  of  the  erection,  when  the  canal  returns  to  its 
original  dimensions,  there  exudes  from  its  anterior  aperture 
(meatus)  a  clear  and  mucous  substance,  which  simply  is  the 
secretion  from  Cowper's  glands. 

The  other  products  of  secretion,  poured  into  the  vacuum 
formed  by  the  dilatation  of  the  urethral  canal,  and  whose 
mixture  dilutes  the  sperm  and  so  assists  in  its  easy  passage, 
come  from  the  racemose  glands  of  Littre  and  the  prostatic 
glands  (little  glandular  pouches  radiating  from  the  urethral 
canal  in  the  posterior  half  of  the  prostate  (Fig.  131,  p.  479) ; 


486  URO-GENITAL  APPARATUS. 

and  are  analogous  to  that  from  Cowper's  glands  and  the 
seminal  vesicles.  The  utriculus  prostaticus  does  not  appar- 
ently furnish  a  special  liquid,  nor  take  an  important  part  in 
the  function  of  reproduction,  but  is  probably  only  a  rudi- 
mentary organ. 

The  spermatic  fluid,  mingling  with  the  product  of  the 
vesiculaB  seminales  by  means  of  the  contraction  of  these 
vesiculaB  and  of  the  efferent  canals,  arrives  at  the  prostatic 
portion  of  the  urethra;  here  its  presence,  by  reflex  irritation, 
sets  up  a  mechanical  action  by  which  it  is  projected  forcibly 
and  with  jerks  outside  of  the  canal ;  in  other  words,  it  is 
ejaculated.  The  forcible  and  jerky  ejaculation  has  been 
generally  attributed  to  the  contractions  of  the  bulbo-cavern- 
ous  muscle,  which  has  been  named  accelerator  seminis  et 
urinm;  but  we  must  remember  that  this  muscle  is  separated 
from  the  m*ethral  canal  by  the  interposition  of  the  bulbous 
portion,  rigid  on  account  of  its  state  of  erection ;  and  that 
moreover  it  is  placed  in  front  of  the  prostate,  or  in  front  of 
the  place  where  the  spermatic  fluid  has  been  poured  in ;  and, 
consequently,  it  is  difficult  to  understand  how  it  can  astiist 
primarily  in  expelling  the  sperm,  though  it  may  possibly  act 
ulteriorly  in  completing  the  ejaculation  of  the  sperm,  in  that 
part  which  lies  between  the  prostate  and  glans  penis. 

At  the  moment  that  the  sperm  is  poured  into  the  prostatic 
portion,  this  portion  of  the  canal  is  isolated  from  the  bladder 
on  account  of  the  erection  of  the  verumontanum  (Fig.  131), 
a  little  eminence  situated  on  the  posterior  wall  of  the  canal, 
and  which  in  its  state  of  turgescence  is  in  contact  with  the 
anterior  wall ;  this  would  then  obstruct  all  communication 
between  the  bladder  and  the  urethral  caniil,  and  we  all  know 
that  micturition  is  impossible  during  the  state  of  erection.  On 
the  other  hand,  the  ducts,  incorrectly  called  ejaculatory,  open 
in  front  of  and  at  each  side  of  the  verumontanum^  so  that  the 
sperm  can  readily  pass  into  the  urethra,  and  All  up  the  whole 
prostati'^/  portion ;  but  it  can  go  no  farther,  because  at  this 
moment  the  so-called  Wilson's  muscle  contracts  and  obliter- 
ates tho  membranous  portion  (Fig.  131,  2).  The  seminal 
fluid  then  accumulates  in  the  straight  part  of  the  canal  com- 
prised between  the  verumontanum  and  the  urethral  sphincter, 
or  Wilson's  muscle  (Fig.  131,  from  1  to  2) ;  here  it  accumu- 
lates under  a  high  pressure,  because  the  contractions  of  the 
smooth  muscles  which  pushed  it  there  (efferent  canal  and 
seminal  vesicles),  though  slow,  are  very  energetic.  It  cannot 
pass  towards  the  bladder  owing  to  the  obstruction  offered  by 


GENITAL  SYSTEM.  487 

the  verui  .orxannm;  it  cannot  immediately  escape  along  the 
canal  on  account  of  the  contraction  of  the  urethral  sphincter. 
But  this  muscle  cannot  long  maintain  its  state  of  contraction  ; 
it  relaxes,  and  immediately,  under  the  influence  of  the  high 
pressure  which  it  has  acquired,  the  seminal  fluid  is  precipi- 
tated, and  forcibly  precipitated ;  then  the  muscle  again  con- 
tracts and  arrests  the  seminal  eruption;  again  suddenly 
relaxes  and  so  on,  so  long  as  the  ejaculation  continues.  We 
see  thus  that  the  force  of  the  ejaculation  is  due  to  the  sudden 
relief  of  the  high  pressure,  and  the  rhythm  to  the  alternate 
contraction  and  relaxation  of  the  urethral  sphincter. 

In  this  view  it  is  seen  that  the  integrity  of  the  pros- 
tate is  as  important  to  the  act  of  generation,  as  it  is  to  that 
of  micturition.  It  is  here  also  the  contacit  of  the  seminal 
fluid  with  the  mucous  surface  which  influences  the  intermittent 
and  tetanic  contraction  of  the  urethral  sphincter.  So,  also,  dis- 
ease of  the  prostatic  mucous  surface  has  a  great  influence  over 
the  function  of  generation,  and  may  cause,  either  satyriasis, 
impotence,  or  seminal  emissions.  This  explains  the  useful- 
ness of  cauterization  (Lallemand)  to  counteract  the  last- 
named  disturbance. 

It  is  interesting  to  note  the  circumstances  which  flivor  the 
movements  and  vitality  of  the  spermatozoids  in  the  ejacu- 
lated seminal  fluid.  Cold  water,  the  electric  spark  (Prdvost 
and  Dumas),  and  acid  solutions  destroy  the  spermatozoids; 
slightly  alkaline  and  neutral  solutions  are  favorable  to  and 
increase  the  activity  of  their  movements.  The  vaginal 
mucus  destroys  them  only  when  it  is  very  acid;  under 
ordinary  circumstances  the  spermatozoids  remain  living  for  a 
long  time  in  the  vagina,  and  Percy  has  collected  them  in  a 
state  of  activity  at  the  neck  of  the  womb,  eigiit  days  after 
the  last  coitus.^  Finally,  according  to  Godard,  the  menstrual 
blood  increases  the  activity  of  their  movements. 

Moreover,  the  spermatozoids  can  live  in  pus,  blood,  and 
various  other  fluids.  Sims  has  often  seen  conception  take 
place  even  during  severe  suppuration  of  the  neck  of  the 
uterus.  According  to  Kolliker  phosphate  of  soda  is  especially 
favorable  to  their  activity. 

.  1  See  Marion  Sims,  "  Notes  Cliniques  sur  ia  Chirurgie  Ute- 
rine."    Traduct.  frangaise,  Paris,  1872. 


488  URO-GENITAL  APPARATUS. 


n.   Female  Organs  of  Generation. 

These  organs  of  generation  are  composed  of  a  gland 
(ovary),  and  excretory  canals  (Fallopian  tube,  womb,  vagina, 
&Q.\  whose  points  of  interest  are  represented,  on  one  hand, 
as  organs  for  copulation  (vagina  and  its  appendages),  and  on 
the  other  hand,  as  a  place  (womb)  where  the  product  of 
fecundation  may  be  developed. 

1.  The  ovary  arises  from  that  germ  which,  as  we  have 
learned,  was  placed  on  the  inner  border  of  the  WolflSan  body 
and  remains  unchanged  until  the  close  of  the  second  month 
of  embryonic  life.  We  have  also  learned  how  this  germ  is 
developed  into  a  testicle.  When,  however,  it  is  destined  to 
develop  into  an  ovary,  the  peritoneal  epithelium,  which 
envelops  the  germ,  sends  offshoots  or  vegetations  in  form  of 
culs  de  sac  or  pouches,  which  penetrate  into  the  deeper  por- 
tions of  the  organ  (Fig.  133)  ;  these  form  true  tubular  glands 

(Fig.  133, 1,  2,  3) ;  but  soon  the 
orifice  of  these  tubular  glands 
is  obliterated  (ic/.,  4,  5),  and 
there  remains  only  a  little  cavity 
{id.^  6)  which  is  lined  with  epi- 
thelium and  is  completely  closed. 
These   very   numerous  cavities 

Fig.i33.-Deveiopngnt^of  theGraa-  constitute  the  Graafian  vesicles 

(Fig.  134) ;  their  epithelium  is 

thus  an  offshoot  from  the  peritoneal  epitiielium. 

2.  The  excietory  canals  are  formed  by  the  development  of 
the  Mullerian  ducts  (p.  478).  The  upper  portion  of  these 
two  ducts  forms  the  Fallopian  tube,  which  is  free  and  un- 
united on  either  side;  the  lower  portion  unites  with  the 
corresponding  portion  of  the  opposite  side  to  form  the  uterus, 
and  an  incomplete  fusion  of  the  two  sides  forms,  in  animals, 
tlie  bifid  uterus  or  double  and  independent  wombs,  as  in  the 
rodents.  Thus  is  seen,  as  the  opposite  of  what  occurs  in  the 
development  of  the  male  organs  of  generation,  that  the  Mul- 
lerian ducts  develop  into  the  female  organs  of  generation, 
and  the  Wolffian  body  becomes  atrophied ;  sometimes,  and 
always  in  the  cow,  the  excretory  canal  of  the  Wolffian  body 

*  00,  Surface  of  the  ovary,  and  its  epithelium,  which  at  1  forms  a  deep 
pouch,  a  sort  of  tubular  glandular  structure :  this  gland  is  gradually  more  and 
more  isolated  at  2,  3,  4,  5 ;  at  6  it  is  completely  separated,  and  forms  a  cavity 
lined  with  epithelium,  which  is  hypcrtropliied  at  one  point  (c/,  Troligerous  disc), 
wherein  one  of  the  cells  has  become  the  ovary  (o). 


FEMALE   ORGANS  OF  GENERATION.  489 

persists  in  a  rudimentary  state,  and  is  known  by  the  name  of 
Gartner's  canal.^ 

The  vagina  alone  has  not  its  homologue  in  man  ;  it  seems  to 
be  a  sort  of  intermediate  territory  between  the  internal  and 
external  organs  of  generation.^ 

The  external  organs  of  generation  originate,  as  in  the  case 
of  man,  from  a  perineal  cleft  which  is  in  connection  with  the 
mucous  surface  of  the  deep-seated  organs ;  only,  whilst  this 
cleft  or  fissure  is  closed  in  man,  and  so  forms  a  canal  (mem- 
branous and  spongy  portion  of  the  urethra)  which  opens 
only  at  its  anterior  and  superior  extremity  (meatus  urinon 
rius)  ;  in  woman  this  fissure  remains  open,  its  boundary  being 
formed  by  two  cutaneous  folds  (labia  mnjora),  which  do  not 
join  together,  but  circumscribe  what  is  called  the  vulvar 
opening.  Thus  it  may  be  seen  that  generally  all  the  genital 
parts  in  women  have  their  homologue  in  man.  The  ure- 
thral canal  of  the  woman  corresponds  to  that  part  of  the 
urethra  of  the  man,  which  extends  from  tlie  neck  of  the 
bladder  to  the  verumontanuni  or  caput  gallinagims  (crista 
urethra)),  u])on  the  summit  of  which,  and.  in  front,  opens  the 
prostatic  utricle  or  male  uterus.^ 

A.   Ovary  and  ovulation.^ 

To  sum  up,  the  ovary  is  an  organ  formed,  in  a  physiological 
sense,  of  cuts  de  sac,  which  become  isolated  and  closed  vesi- 
cles, and  are  lined  with  globular  or  spheroid  epithelium.  We 
shall  find  that  there  are  three  distinct  kinds  of  epithelium  in 
three  grand  divisions  of  the  female  organs  of  generation ; 
viz.,  the  globular  form  in  the  ovary,  the  vibratile  columnar 
in  the  uterus,  and,  lastly,  the  tessellated  pavement  in  the 
vagina. 

The  physiology  of  these  organs  shows  that  the  epitheliums 
are  the  most  important  of  their  elements ;  with  scarcely  any 
activity  in  infancy  and  youth,  at  the  period  of  puberty  the 

^  See  FoUin,  "  Recherches  sur  les  Corps  de  Wolff."  Th^se 
Inaugurale.     Paris,  1850. 

2  See  A.  Courty,  "  Maladies  de  1' Uterus,  des  Ovaires,  et  des 
Trompes.     Notions  Prelimiuaires."     Second  edition,  1870,  p.  74. 

8  Kolliker,  "  Eutwickelungsgeschichte  des  Menscheu  und  der 
hoheren  Thicre."     Leipzig,  18G1. 

"*  The  importance  of  the  ovarian  function  and  its  anomalies  may 
be  found  by  reference  to  Albert  Puech,  "  Des  Ovaires,  de  leurs 
Anomalies,"  in  "  ^Montpellicr  Medical."     187-}  and  1873. 


490 


URO-GENITAL  APPARATUS. 


function  of  these  epitheliums  is  suddenly  developed;  the 
ovarian  epithelium  gives  the  signal  and  ovulation  ensues ;  the 
epithelium  of  the  uterus,  next,  becomes  very  active  either  in 
the  form  of  simple  menstruation,  or  of  gestation  ;  lastly,  the 
vaginal  epithelium  as  well  as  its  appendages  (external  genital 
organs)  does  not  remain  quiescent. 

As  the  ovary  is  the  seat  of  origin  for  most  reflex  and 
pathological  phenomena  we  will  commence  our  study  with 
that  organ. 

The  ovisacs  or  Graafian  vesicles  are  formed  of  a  little 
l)ouch  of  connective  tissue,  on  whose  inner  surface  a  thick 


Fig.  1^. 
Graafian  vesicle  enclosing  an  ovum.* 


F\g.  135.— Oram.t 


layer  of  small  globules  are  found  {memhrana  granulosa^  Fig. 
134)  ;  at  one  point  this  layer  is  a  little  thicker  aud  forms  the 
so  called  proligerons  disc  (G).  One  of  these  globules  (E) 
of  the  proligerous  disc  becomes  developed  to  a  considerable 
size,  being  summoned  to  a  higher  destiny  than  its  com- 
panions, and  foi-ms  the  ovum,  the  most  perfect  type  of  the 
cellular  condition  (Fig.  135)  ;  the  ovum  attains  a  size  of  ^ 
or  ^^  of  a  millimetre,  and  may  be  visible  to  the  naked  eye. 


♦  A,  B,  Fibrous  layers  of  the  vesicle.  C,  Membrana  granulosa.  G,  Tunica 
granulosa  or  proligerous  disc,  with  the  ovum.  1,  Vitelline  membrane.  2,  Vitel- 
lus  or  yelk.    3,  Genninal  vesicle  of  Purkinje. 

t  A,  Nucleolus,  or  germinal  spot.  B,  Nucleus,  or  genninal  vesicle.  C,  Yelk, 
D,  Vitelline  membrane,  or  lona  pelluciila. 


FEMALE  ORGANS   OF  GENERATION.  491 


Sometimes  two  ova  are  found  in  a  Graafian  vesicle  (Bischoff/ 
Davaine  ^).  This  ovum  is  composed  of  a  cellular  envelope 
or  vitellme  membrane  (or  chorion,  D),  having  protoplasmic 
contents  or  yelk  (vitellus)  (Fig.  185,  C)  ;  we  must  not,  how- 
ever, confound  this  yelk  with  the  entire  yellow  part  of  a 
bird's  Q^g ;  the  latter  contains  the  eg'g  of  mammalia,  as  its 
tread  or  cicatricula^  andj  in  addition,  a  great  mass  of  nutrient 
material,  the  yellow,  properly  so  called ;  a  nucleus  or  ger- 
minal vesicle  (B),  which  contains  inside  a  nucleolus  or  ger- 
minal spot  (A),  is  always  found  in  the  vitellus. 

Not  all  the  Graafian  vesicles  of  an  oyary  arrive  simulta- 
neously at  this  degree  of  development,  nor  do  they  contain 
all  their  ova  in  a  state  of  maturity. 

It  is  only  at  the  commencement  of  the  period  of  puberty, 
or,  more  correctly,  at  each  menstrual  period,  that  one  or  two 
ovisacs  (Graafian  vesicles)  are  perfectly  developed.  At  this 
time  one  of  the  Graafian  vesicles,  usually  that  next  the  sur- 
face of  the  ovary,  is  swollen,  its  contents  augment,  and  it  be- 
comes more  marked  ;  that  portion  of  its  wall  nearest  the  sur- 
face of  the  ovary  presses  against  this  surface ;  at  this  point 
occurs  an  arrest  of  nutrition,  and  consumption  of  its  own 
walls;  this  condition,  assisted  by  an  increasing  swelling  of 
the  central  portion  of  the  ovary  {stroma  or  spongy  portion 
of  the  ovary)  readily  induces  a  rupture  of  such  a  nature  that 
the  contents  of  the  ovisac  escape,  bringing  out  the  ovum  with 
the  debris  of  the  proligerous  disc.  Usually  this  is  the  most 
favorable  moment  for  fecundation  of  the  ovum  by  the  arrival 
of  the  spermatozoids,  if,  perchance,  these  latter  have  been 
introduced  into  the  female  genital  organs;  but  whether  the 
ovum  is,  or  is  not  fecundated,  the  appendages  of  the  uterus 
act,  in  a  mechanical  point  of  view,  almost  in  the  same  man- 
ner. 

After  the  expulsion  of  the  largest  part  of  its  contents,  the 
Graafian  vesicle  closes  again  and  undergoes  a  cicatricial 
healing  of  its  ruptured  envelope,  leaving  but  a  slight  trace  of 
its  rupture ;  it  has  also  a  yellow  color  received  from  the  blood 
pigment,  arising  from  a  slight  hemorrhage  which  accompanies 

*  Bischoff,  *'  Traitd  du  Developperaent  de  1' Homme  et  des 
Mamraiferes,"  suivi  de  I'histoire  du  developpement  de  I'oeuf  du 
lapin.  Translated  from  the  German  by  A.  J.  L.  Jourdan.  Paris, 
1843. 

^  Davaine,  "  Memoires  sur  les  Anomalies  de  I'CEuf."  Paris, 
18(il,  8vo,  with  illustrations. 


492  URO-CENITAL  APPARATUS. 

its  rupture.  It  is  a  most  wonderful  fact  that,  if  the  ovum 
does  undergo  fecundation,  arrives  in  the  uterus,  and  gestation 
occurs,  there  is  produced  in  the  ovary,  by  some  mysterious 
and  sympathetic  reflex  action,  a  hypertrophied  evolution 
of  the  ruptured  ovisac ;  to  this  hypertrophy  an  atrophy  ulti- 
mately succeeds  (at  the  close  of  pregnancy),  which  gives 
rise  to  a  cicatrix  analogous  to  the  preceding,  but  much  larger 
and  more  enduring.  These  cicatrices  are  called  corpora 
lutea  (corpus  luteum,  a  yellow  body)  :  the  first  are  called 
yellow  bodies  of  menstruation.,  ov  false  yellow  bodies;  the 
others  are  called  yellow  bodies  of  fecundation  (of  pregnancy), 
or  true  yellow  bodies, 

B.  Fallopian  tube.,  womb,  and  tnenstruation. 

The  ovum  expelled  from  the  ovary  then  falls  outside  that 
organ ;  it  may  fall  into  the  peritoneum  and  there  disappear, 
and,  in  case  of  fecundation,  may  there  undergo  a  development 
(peritoneal  pregnancy);^  but  this  is  not  the  noi-mal  course: 
in  the  physiological  conditions,  ovulation  is  accompanied  with 
particular  phenomena  which  cause  tlie  ovum  to  fill  into  the 
fimbriated  extremity  of  the  Fallopian  tube  or  oviduct.  The 
Fallopian  tube  is  a  movable,  contractile,  and  erectile  organ. 
The  contractility  of  this  tube  and  that  of  the  smooth  muscu- 
lar fibres  which  are  found  in  the  broad  and  ovarian  liga- 
ments, must  favor  the  application  of  the  orifices  of  the 
Fallopian  tubes  to  the  ovary  (Ch.  Rouget) ;  yet,  its  erection 
has  also  some  influence  in  this  act,  since  there  is  sufficient 
erectile  tissue  arranged  in  such  a  manner  that  when  in  a  state 
of  turgescence  the  fimbriated  extremity  of  the  Fallopian  tube 
would  be  made  to  embrace  in  its  cavity  the  whole  ovary. 
The  ovum  thus  falls  into  the  end  of  the  Fallopian  tube, 
whence,  by  means  of  the  movements  of  the  ciHated  epithelium, 
and  on  account  of  the  peristaltic  contractions  of  this  oviduct, 
it  is  passed  along  into  the  womb;  at  this  latter  place  it  sets 
in  action  certain  phenomena  if  the  ovum  has  been  fecundated, 
or  if  it  is  non-fertilized  it  is  thrown  off  with  the  catamenial 
or  menstrual  flow. 

It  has  been  recognized,  in  fact,  that  the  fall  of  the  ovum 
coincides  almost  exactly  with  the  menstrual  period  ^  (every 

'  See  Th.  Keller,  "  Des  grossesses  Extra-ut6rines  (avec  deux 
observations  de  Koeberle).     These  de  Paris,  1872,  No.  157. 

'-^  See  Pouchet,  "  Ovulation  Spontanee  et  Fecoudation."  Paris, 
1817. 


FEMALE  ORGANS  OF  GENERATION.  493 

28  clays  on  the  average).  The  fall  of  the  Qg^^  consequently, 
is  periodical ;  this  phenomenon  is  accompanied  with  other 
accessory  phenomena,  called  molimina  menstrualia^  which 
consist  of:  a  congestion  of  the  spinal  cord,  pain  in  the 
lumbar  region,  phenomena  of  eccentric  sensibility,  pains  at 
the  surface  which  should  be  referred  to  the  spinal  cord; 
finally,  the  uterine  phenomena,  menstrual  hemorrhage^  catOr- 
menial  flow. 

The  catamenial  flow  should  be  carefully  examined,  as  we 
shall  discover  a  phenomenon  which  is  essentially  epithelial. 
The  uterus,  a  muscular  organ  to  be  sure,  but  whose  muscular 
element  displays  its  important  function  only  during  or  at  the 
close  of  gestation,  presents  a  cavity  which  is  lined  with  a 
mucous  surface ;  this  lining  is  really  only  a  vihratile  columnar 
epiiheliumy  almost  immediately  attached  to  the  muscular 
element,  with  scarcely  any  substratum  of  connective  tissue 
like  the  corium  in  the  skin.  This  epithelium  is  quite  abun- 
dant, is  endowed  with  a  good  deal  of  activity,  and  forms 
by  its  deep  vegetations,  tubular  glands  analogous  in  appear- 
ance to  the  glands  of  Lieberkiihn,  and  which  are  imbedded 
in  the  muscular  walls ;  we  shall  see  that  at  the  moment  of 
fecundation  this  epithelium  forms  enormous  papillary  vegeta- 
tions which  give  origin  to  the  decidua :  in  pathology  it  is 
frequently  the  source  of  a  large  number  of  uterine  neoplasms. 
More  remarkable,  however,  than  these  is  the  fact  that  this 
epithelium  is  subjected  to  a  sort  of  monthly  moulting,  exactly 
coincident  with  ovulation ;  a  similar  fact  is  observed  in  the 
heat  or  rutting  of  female  mammalia.  Now  as  this  epithelial 
lining  protects  or  covers  the  uterine  muscle,  which  is  quite 
vascular  and  even  erectile,  it  happens  that  the  epithelial  shed- 
ding exposes  a  large  number  of  little  vascular  canals ;  which 
burst  under  the  influence  of  the  general  turgescence  of  the 
organs  at  this  moment,  and  occasion,  especially  in  woman,  a 
more  or  less  abundant  hemorrhage.  Thus  though  the 
hemorrhage  would  seem  to  be  the  most  important  phenom- 
enon, it  is  none  the  less  true  that  the  very  essence  of  men- 
struation is  an  epithelial  moulting,  sympathetic  with  the  epi- 
thelium development  in  the  ovary,  and  whence  results  the 
shedding  of  the  ova  or  ovulation. 

It  is  unnecessary  to  state  that  at  this  period  of  the  men- 
strual hemorrhage  the  vessels  themselves  exercise  no  especial 
function :  at  this  time  there  are  certain  moditications  of  the 
vaso-motor  innervation  that,  unless  the  blood  is  thrown  off 
from  the  uterine  surface,  the  hemorrhagic  flux  will  be  accom- 


494  URO-GENITAL  SYSTEM. 

plished  by  other  vessels.  Of  this  nature  are  the  nasal,  pul- 
monary, and  intestinal  hemorrhagies,  which  sometimes  occur 
in  women  at  the  catamenial  period.  Recently  a  case  has  been 
reported  (Tueffard,  Un.  Med.,  1872)  of  a  woman  whose  breasts 
every  month  were  the  seat  of  a  painful  swelling,  followed  by 
a  dribbling  at  first  of  serous  fluid,  then  bloody,  which  con- 
dition lasted  during  eight  days. 

Vagina.  —  The  pavement  epithelium  of  the  vagina  and  of 
the  neck  of  the  womb  is  not  inactive  during  the  phenomenon 
of  menstruation  :  an  epithelial  desquamation,  upon  a  smaller 
scale,  occurs  in  these  places  also,  in  consequence  of  which 
occurs  a  thick  whitish  product.  In  certain  frequent  and 
pathological  conditions  this  desquamation  is  permanent,  and 
forms  a  white  or  yellowish  discharge,  commonly  known  as 
"whites,"  or  leucorrhoea^  from  the  vagina,  and  especially 
from  the  neck  of  the  womb. 

The  external  genital  organs  likewise  give  off  an  analogous 
epithelial  desquamation,  but  more  nearly  resembles  a  seba- 
ceous product,  or  more  like  the  smegma  prcBputialis. 

The  vagina  and  the  external  genital  organs  especially  serve 
for  the  purposes  of  copulation,  whose  object  is  fecundation. 


m.    FECUNDATION  AND  DEVELOPMENT   OF  THE 
FERTILIZED  OVUM. 

I.   Fecundation. 

Fecundation  is  the  result  of  the  encounter  of  the  ovum  and 
sperjnatozoids.  We  know  that  the  male  organ  is  arranged 
for  the  ejaculation  of  sperm.  The  female  organs  destined  to 
receive  this  are : 

a.  External  genital  organs.,  which  have  erectile  organs 
(hulbus  vestibuli  seu  vagince^  and  cavernous  body  of  the 
clitoris)^  rudimentary  but  analogous  to  those,  of  the  man ; 
these  organs,  and  especially  the  region  of  the  clitoris,  analo- 
gous to  the  glans  penis,  are  the  principal  seat  of  voluptuous 
venereal  sensations :  — 

b.  The  vagina,  at  the  entrance  to  which  (between  the 
labia  minora  and  the  carunculoB  myrtiforrnes)^  open  on 
either  side  the  excretory  duct  of  the  two  glands  of  Bartolini ; 
which  are  analogous,  both  from  their  secretion  and  product, 
to  Cowper's  glands,  which  we  studied  in  the  male.  Their 
product  seems  to  lubricate  the  entrance  to  the  vagina.   These 


FECUNDATION.  495 

glands  are  interesting  in  a  pathological  point  of  view ;  here 
is  the  seat  in  woman  of  an  inflammation  analogous  to  gonor- 
rlioea  in  man :  in  these  cases  there  is  never  vaginitis :  gonor- 
rhoea in  woman  should  be  translated  Bartholinitis. 

The  vagina  is  essentially  the  organ  of  copulation :  its  ridges 
and  transverse  rugae  excite  to  the  highest  state  the  sensi- 
bility of  the  glans  and  induce  the  reflex  phenomenon  of  ejacu- 
lation :  in  the  vagina  are  let  loose  the  spermatozoids.  The 
condition  of  its  mucous  surface  influences  the  vitality  of  these 
fertilizing  elements:  an  acid  secretion  is  fatal  to  these  vibratile 
filaments ;  whilst  an  alkaline  mucus,  like  the  ordinary  product 
of  the  pavement  epithelium  of  the  neck  of  the  womb,  is  emi- 
nently favorable  to  the  vitality  and  movements  of  the  sper- 
matozoids (see  p.  567). 

It  is  not  necessary  that  the  voluptuous  sensations  which 
in  man  accompany  the  ejaculation  of  sperm  during  coitus 
should  exist  in  women  for  the  induction  o^ fecundation  ;  the 
sole  conditions,  fulfilled  by  the  external  organs  of  generation 
in  the  woman,  is  to  allow  the  introduction  of  seminal  fluid 
into  the  vagina  and  to  hold  it  there.  The  hymen,  which 
always  presents  a  perforation  of  variable  form  (semi-lunar, 
horse-shoe,  annular,  or  bilabial  hymen),  opposes  no  obstacle 
to  this  introduction,  and  ordinarily  the  hymeneal  membrane 
is  broken  at  the  first  contact;  but  oftentimes  this  membrane 
presents  a  very  defined  sensibility,  which,  set  in  action  by  the 
slightest  touch,  induces  by  reflex  action  an  energetic  contrac- 
tion of  the  vaginal  sphincter,  a  contraction  which  is  accom- 
panied by  violent  pain,  and  opposes  an  obstacle  to  coitus. 

This  curious,  in  its  physiological  aspect,  phenomenon  has 
been  examined  by  Mar.  Sims  (of  New  York),  under  the  name 
oi  vaginismus ;  quite  reasonably,  Sims  compares  vaginismus 
with  blepharismus  (nictation),  or  spasmodic  and  painful  con- 
traction of  the  orbicular  muscle  of  the  eyelids,  accompanied 
with  an  extreme  sensibility  to  light,  or  photophobia.  This 
surgeon  has,  moreover,  demonstrated  that  vaginismus  cannot 
be  abolished  nor  modified  by  forcible  or  gradual  dilatation, 
so  long  as  it  is  concerned  with  the  origin  of  the  reflex  irrita- 
tion, that  is,  with  the  hymen  or  its  remains  (carunculaB  myr- 
tiformes)  ;  but  that  excision  and  cauterization  of  these  sensi- 
tive membranes  (especially  on  their  external  surface)  cause 
an  immediate  disappearance  of  these  spasmodic  contractions, 
which  were  the  cause  of  the  hyperaBSthesia. 

On  account  of  the  fact,  that  the  aperture  of  the  meatus 
ui'inarius  of  the  glans  during  erection  has  a  vertical,  and  that 


496  URO-GENITAL  SYSTEM. 

of  the  neck  of  the  womb  a  transverse,  position,  it  is  possible 
that  the  spermatic  fluid  should  be  thrown  directly  into  the 
uterus.  This  passage  would  be  more  readily  accomplished 
by  the  state  of  erection  of  the  uterus  and  its  neck,  on  account 
of  the  opening  being  thereby  enlarged;  it  has  been  said  that 
this  erection  would  dilate  the  cavity  and  thus  induce,  on  the 
part  of  the  womb,  a  true  aspiration  of  the  sperm.  However, 
direct  observation  in  animals  (the  rabbit)  shows  that  the 
spermatic  fluid  is  only  thrown  into  the  vagina. 

According  to  the  researches  of  Arm.  Despres  (Acadcmie 
de  Medecine,  Decembre,  1869)  :  "The  neck  of  the  womb  is 
furnished  with  racemose  or  tubular  glands  placed  in  a  portion 
of  the  muscular  tissue  of  the  womb,  like  the  prostatic  glands 
in  the  midst  of  muscular  fibres  in  the  prostate.  These  glands 
secrete  a  clear,  viscous,  and  albuminous  fluid,  analogous  to 
the  prostatic  fluid,  which  flows  from  the  neck  in  an  intermit- 
tent manner,  and  produces  the  ejaculation  in  the  woman. 
This  fluid  slowly  flows  from  the  neck  of  the  womb  and 
remains  upon  the  os  uteris  and  in  the  cavity  of  the  neck:  this 
ejaculation  in  the  woman  is  destined  to  provide  a  vehicle  for 
the  zoosperms^  and  allows  them,  to  arrive  icith  certainty  into 
the  neck  of  the  wotnh} 

Under  these  circumstances  it  is  incontestable  that  the 
peculiar  movements  of  these  vibratile  elements  themselves 
form  the  essential  condition  of  their  meeting  with  the 
ovum :  occasionally  it  is  only  necessary  to  deposit  the  sper- 
matozoids  at  the  vulvar  aperture,  and  these,  by  their  own 
movements,  seek  the  ovum  by  following  the  vaginal  j)assage, 
through  the  neck  and  the  body  of  the  womb,  and,  finally,  the 
Fallopian  tube.  It  is  known,  also,  that  a  small  quantity  of 
sperm  from  the  male  frog,  deposited  at  the  end  of  one  of 
the  long  strings  of  eggs  which  these  animals  lay,  has  fertilized 
even  the  last  ova  at  the  other  end  of  the  chain. 

The  encounter  of  the  spermatozoids  with  the  ovum,  or 
fecundation^  occurs  even  in  the  ovary,  or  at  the  fimbriated 
extremity  of  the  Fallopian  tube,  as  has  been  proved  by 
peritoneal  or  tubal  conception  and  pregnancy. 

The  phenomenon  of  fecundation  results  from  the  penetra- 
tion of  the  spermatozoids  into  the  substance  of  the  ovum, 
where  they  dissolve  and  disappear.   It  is  diflicult,  on  account 

*  Arm.  Despr^s,  "  Etudes  sur  quelques  Points  de  1' Anatomic  et 
de.la  Physiologic  du  Col  de  I'Ut^rus."  ("  Bulletin  de  I'Acad.  de 
M6decine,  18G9,  Vol.  XXXIV.  p.  1131.) 


FECUNDATION.  497 

of  the  thickness  of  the  vitelline  membrane,  to  comprehend 
this  penetration ;  though  in  a  number  of  the  lower  animals 
pores  or  canaliculi  have  been  observed,  which  might  afford 
a  passage  for  the  fecundating  element  {rnicropyle). 

In  a  recent  work  ^  on  fecundation  and  development  of  the 
ovum  in  rabbits,  Weil  has  assured  himself  that  spermatozoids 
do  penetrate  into  the  very  substance  of  the  ovum.  He  also 
states  that  they  preserve  their  active  movements  for  several 
hours  after  their  passage  through  the  vitelline  membrane. 
He  has  not  only  seen  them  during  the  separation  of  the  cells 
from  the  vitellus  after  its  segmentation,  but  even  inside  the 
protoplasm  of  the  vitelline  cells.  At  this  latter  place  the 
spermatozoids  lose  their  outline  and  disappear.  An  examina- 
tion of  all  the  evidence  presented  would  apparently  prove, 
that  fecundation  (conception)  essentially  consists  in  a  fusion 
of  the  spermatozoid  with  the  female  element.  This  view  is 
also  supported  by  the  comparative  study  of  fecundation  in 
the  lower  vegetable  life  (in  the  spirogyra^  for  instance). 

Under  the  exciting  influence  of  the  fecundated  or  fertilized 
ovum  in  its  course  of  development,  the  uterine  epithelium  is 
the  seat  of  wonderful  changes.  The  mucous  tissue  forms 
large  pouches,  and,  so  soon  as  the  ovum  comes  into  the  womb, 
it  is  lodged  in  a  valley  formed  by  two  of  these  pouches  or 
villi ;  then  these  latter  grow  in  every  direction  and  finally 
completely  enclose  the  ovum,  so  that  a  perfect  envelope 
called  the  caduca  (Fig.  136,  c,  ee,  f,  A;),  or  memhrana 
decidua  is  formed  around  it.  The  whole  of  the  lining 
mucous  surface  of  the  uterus  is  called  the  caduca;  that  por- 
tion which  lines  the  uterus  is  called  uterine  caduca  or  decidua 
vera  (Fig.  136,  c)  ;  that  which  forms  a  complete  envelope  of 
the  Q^  is  cdMedi  foetal  caduca  or  decidua  reflexa  (ee,/)  ;  that 
surface  of  this  decidua  reflexa  which  is  continuous  with  the 
first-named  (that  is,  the  very  point  of  attachment  of  the  e^^ 
to  the  uterus)  is  called  the  caduca  serotina,  or  decidua  sero- 
tina  (Fig.  136,  ee),  in  accordance  with  false  ideas  formerly 
held  in  regard  to  its  mode  of  development.  The  placenta 
(Fig.  136  and  143)  is  formed  near,  and  partially  at  the 
expense  of,  the  caduca  serotina. 

The  muscular  portion  of  the  uterus  also  undergoes  hyper- 
trophy, and  forms  new  (smooth)  muscular  elements,  simul- 
taneously with  the  enlargement  of  preexisting  fibres.  Finally, 
the  vessels  partake  of  this  increase  of  development,  as  increased 

»  C.  Weil,  in  Strieker's  "  Medic.  Jahrbucher,  1873. 
32 


498 


URO'GENITAL  SYSTEM. 


vascularization  by  arteries  and  veins  is  required  for  the  nu- 
trition of  the  new  being  undergoing  process  of  development. 
An  increase  of  the  muscular  elements  is  required  for  the 
process  of  expulsion  (parturition,  or  labor)  of  the  new  being, 
when  perfectly  developed  (foetus  at  full  term  of  pregnancy). 
It  is  sufficient  to  state  that  this  act,  like  all  those  heretofore 


Fig.  136.  —Womb,  egg,  and  membranes.* 

studied,  is  under  the  influence  of  the  nervous  system  ;  we  shall 
Bee  here  also  reflex  phenomena  analogous  to  all  those  which 
concern  expulsion  and  excretion.  The  point  of  origin  for  these 
phenomena  is  normally  in  the  uterus ;  but  various  excitations 


*  Vertical  section  of  the  womb,  containing  a  developed  egg  or  ovum,  a.  Neck, 
filled  with  a  gelatinous  plug.  66,  Orifice  of  the  Fallopian  tubes,  cc^  Membrana 
decidua  vera,  d,  Uterine  cavity,  almost  entirely  filled  with  the  ovum,  ee.  Where 
the  decidua  vera  is  continuous  with  the  decidua  reflexa.  f,  Caduca  serotina  or 
placenta,  g,  Allantols.  h.  Umbilical  vesicle  and  its  pedicle  in  the  umbilical 
cord,    ij  Amnion,    k,  Decidua  reflexa  and  chorion. 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      499 

can  occasion  it  in  parts  even  at  a  distance  from  the  {)elvic 
organs.  Certain  investigations  on  rabbits  (W.  Schlesinger) 
show  that  excitations  of  the  central  portion  of  the  spinal 
nerves  induce  uterine  contractions ;  and  the  same  effect  has 
been  caused  by  excitations  of  the  central  portion  of  the 
pneumo-gastric ;  moreover,  clinical  observation  has  shown 
that  a  mechanical  irritation  of  the  breasts  favors  uterine 
contractions. 

n.   Development  op  the  Fecundated  Egg. 

The  result  of  fecundation  in  the  ovum  consists  of  segmen- 
tation of  the  mtellus.  We  commenced  our  studies  with  the 
globular  proliferation  (p.  10) ;  this  is  a  type  of  one  of  the 
manifestations  of  the  general  characteristics  of  the  globules, 
consisting  of  segmentation  and  reproduction.  Simple  seg- 
mentation can  sometimes  occur  without  fecundation;  but, 
generally,  the  presence  of  the  spermatozoids  seems  to  set  in 
action  a  physiological  excitation  which  induces  the  division 
of  the  vitelline  protoplasm ;  in  every  case  of  segmentation 
of  the  unfertilized  ovum,  this  segmentation  does  not  extend 
very  far,  and  never  forms  the  blastodermic  membrane, 

I.  Envelopes  of  the  embryo^  respiration^  nutrition. 

These  envelopes  vary  according  to  the  period  of  the 
development  of  the  embryo ;  and,  since  they  are  the  seat  of 
the  exchanges  between  the  foetal  organism  and  its  external 
medium  (maternal  organism),  the  manner  in  which  these 
exchanges  (nutrition  and  respiration)  are  performed  depends 
upon  the  different  periods  of  the  embryonic  life. 

First,  After  the  fecundated  egg  has  traversed  the  tubal 
canal,  and  segmentation  of  the  vitellus  has  occurred,  the  Q^<g 
has  no  other  envelope  than  its  vitelline  membrane  (see  Fig. 
137)  upon  whose  surface  little  homogeneous  villi  are  devel- 
oped ;  these  constitute  the  first  chorion  (Fig.  137,  1).  By 
the  process  of  osmosis  and  imbibition,  the  albuminous  liquids 
in  the  Fallopian  tube  and  the  uterine  cavity  pass  through 
this  membrane,  and  are  borne  along  with  the  segmentation 
of  the  vitellus. 

Secondly,  when  the  segmentation  is  completed,  and  the 
blastoderm  is  formed,  the  relations  between  parent  and 
embryo  are  more  regularly  established  by  the  formation  of 
new  envelopes  and  aplaceiita  ;  but,  in  the  human  species,  at 
this  transitional  period,  there  is  established  a  mode  of  nutri- 


500  URO-GENITAL  SYSTEM. 

tion,  which  is  more  durable  than  in  the  ovipara,  which  has 
its  source  from  an  organ  called  the  umbilical  vesicle  ;  finally, 
when  the  body  of  the  embryo  is  developed  it  is  protected  in 


5 

Fig.  137.  —  Commencement  and  development  of  the  e^* 

a  pouch  or  diverticulum,  amnion^  whose  fluid  contents  ward 
off  sudden  compressions. 

Umbilical  vesicle.  When  the  blastoderm  (see  p.  17)  is 
formed  around  the  e^g^  by  its  simple  nutrition,  as  above 
shown,  it  attains  a  considerable  size,  from  the  fact  that  its 
interior  forms  a  cavity,  whilst  the  division  of  the  blastoderm 
into  three  folds  (w,  a)  becomes  more  pronounced  at  that 
place  in  which  the  body  of  the  embryo  will  be  formed  (Fig. 
138).  But  as  the  embryo  becomes  gradually  developed,  the 
circular  region,  by  which  it  forms  a  part  of  the  common 
blastodermic  vesicle,  gradually  recedes  (from  9  to  al.  Fig. 
139)  in  such  a  manner,  that  soon  the  primary  cavity  becomes 
divided  into  two  secondary  cavities  (Fig.  137,  o  and  12),  one 
of  which  forms  a  portion  of  the  embryo  (12),  its  future 
intestinal  cavity  (see  pp.  184,  232,  and  424),  and  the  other 
forms  a  vesicle  placed  above  the  ventral  portion  of  the 
embryo  (Fig.  137,  o),  the  umbilical  vesicle,  which  communi- 
cates with  the  intestine  only  by  a  canal  called  the  omphalo- 
mesenteric duct  (Fig.  139  and  140) ;  the  place  at  which  this 

*  1,  Vitelline  membrane.  2,  External  layer  of  the  blastoderm.  3,  Middle 
layer.  4,  Internal  layer  of  the  blastoderm.  5,  Form  of  the  embryo.  6,  Cephalic 
fold  of  the  amnion.  7,  Caudal  fold  of  the  amnion.  8,  Extremity  of  the  ce- 
phalic fold,  which  tends  to  join  the  corresponding  extremity  of  the  caudal  fold. 
9,  Point  for  formation  of  heart.  10,  Umbilical  vesicle,  yolk  sac.  12,  A  portion 
of  the  internal  fold  of  the  blastoderm,  from  which  the  iiutestiue  will  be  formed. 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      501 

duct  is  continuous  with  the  intestine  is  the  intestinal  umbi- 
licus^ and  the  walls  of  the  body  which  close  around  this  duct 
form  the  cutaneous  umbilicus,  or  navel  (see  p.  231,  Fig. 
64). 

The  umbilical  vesicle  contains  a  fjitty  albuminous  fluid 
which  represents  all  the  extra-embryonic  portion  of  the 
vitellus.  This  liquid  serves  for  the  nutrition  of  the  mam- 
malian foetus  until  the  placenta  is  developed.  The  absorption 
of  the  fluid  of  the  umbilical  vesicle  is  accomplished  by  a 
system  of  blood-vessels  {primary  circulatio7i,  see  farther  on), 


Fig.  138. 


—  Blastodermic 
vesicle.* 


Fig.  139.  —  Egg  with  its  timbilical  vessel 
fuUy  developed.t 


which  are  developed  in  the  external  wall  of  the  vesicle 
(omphalo-mesenteric  vessels) ;  these  absorb  the  contents  of 
this  cavity  by  the  medium  of  the  internal  epithelial  surfjice 
of  the  vesicle,  just  as  in  adult  life  the  mesenteric  vessels 
(vena  porta)  absorb  the  contents  of  the  intestinal  canal  by 
the  medium  of  the  villous  epithelium,  (and  indeed  fine  vas- 
cular villi  are  often  found  on  the  internal  surface  of  the 
umbilical  vesicle). 


*  D,  Yellow,  S,  Vitelline  membrane,  m,  Membrane  at  the  external  layer  of 
the  blastoderm,    a,  Middle  layer,    y,  Internal  layer. 

t  1,  Vitelline  membrane.  *  2,  External  layer  of  the  blastoderm.  3,  Middle 
layer  of  the  blastoderm.  4,  Internal  layer.  5,  Body  of  the  embryo.  6,  7,  8,  9, 
As  in  Fig.  137.  o,  Umbilical  vesicle,  al,  Allantoicf  pouch  or  protuberance,  a, 
Amniotic  cavity. 

In  this  Figure,  as  in  Figs.  137,  140,  141,  the  interrupted  lines  show  the  parts 
belonging  to  the  internal  layer  of  the  blastoderm  ;  the  black  lines  belong  to  the 
mitldle  layer ;  the  dotted  lines  belong  to  the  external  layer. 


502  URO-GENITAL  SYSTEM. 

Yet,  the  existence  and  functions  of  the  umbilical  vesicle, 
or  yolk  sac,  do  not  continue  for  any  great  length  of  time  in 
the  mammalia.  The  nutritive  pabulum  enclosed  by  it  is  not 
large ;  even  at  the  fourth  week  the  umbilical  vesicle  begins 
to  atrophy,  and  towards  the  fifth  only  a  trace  of  it  remains 
(Fig.  142).  In  the  ovipara,  however  (especially  in  birds), 
the  umbilical  vesicle  lasts  much  longer,  and  plays  a  more 
important  part  in  the  nutrition  of  the  chick ;  it  contains  the 
yellow  substance^  a  provision  which  is  sufficient  for  the  devel- 
opment of  the  chick  in  the  Qg'^f^  and  feeds  it  even  after  the 
chicken  is  hatched,  but  at  that  time  it  is  enclosed  inside  the 
abdominal  cavity,  until  the  chicken  is  able  to  feed  himself. 

Amnion.  As  soon  as  the  umbilical  vesicle  and  the  body 
of  the  embryo  have  been  completely  separated  by  the  stran- 
gulation that  we  have  already  studied  (intestinal  and  cuta- 
neous umbilicus),  the  distinction  between  the  three  layers  of 
the  blastoderm  becomes  more  and  more  complete,  and  the 
external  one  gives  rise  to  a  particular  formation,  the  amnion 
and  secondary  chorion.  In  fact,  as  soon  as  the  cutaneous 
umbilicus  is  formed,  and  at  the  same  point,  the  external  fold 
(cutaneous)  of  the  blastoderm  extends  in  such  a  way  as  to 
surround  the  embryo,  and  forms  two  lateral  layers  which 
tend  to  unite  at  its  dorsal  region,  forming  at  the  two  extrem- 
ities two  hood-like  folds  {cephalic  and  caudal^  Fig.  137,  6,  7) 
which  cover  its  caudal  and  cephalic  portions.  Only  the 
middle  portion  of  the  back  of  the  embryo  remains  uncovered, 
but  soon  these  folds  and  layers  by  process  of  development 
unite  (Fig.  137,  8),  until  the  only  opening  {amniotic  umbili- 
cus,  Fig.  139,  8)  is  circumscribed  and  completely  closed, 
p^rom  this  time  the  embryo  is  enclosed  in  a  cavity,  amniotic 
cavity  (Fig.  139,  a),  in  which  it  is  suspended  in  the  ambient 
fluid,  amniotic  fluid,  given  out  from  the  walls  which  form 
this  cavity. 

The  internal  surface  of  the  amniotic  cavity  is  formed  by 
that  entire  portion  of  the  external  layer  of  the  blastoderm, 
which  has  been  isolated  from  the  rest  of  this  fold  by  the  suc- 
cessive hood-like  covering  of  the  embryo  and  the  union  of 
the  amniotic  umbilicus.  This  surface  is  covered  by  an  epi- 
thelial layer  given  off  from  a  layer  of  embryonic  connective 
tissue  (from  the  middle  fold),  in  which  smooth  muscular 
fibres  may  be  seen  (Fig.  140,  141,  dark  and  dotted  lines). 
On  account  of  this  formation  the  rest  of  the  external  fold  of 
the  blastoderm  is  henceforward  completely  isolated  from  the 
body  of  the  embryo,  and  forms  an  extended  envelope  sub- 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      508 

jacent  to  the  primary  chorion  (to  the  vitelline  membrane), 
and  encloses  all  the  appendages  (amnion,  foetus,  umbilical 
vesicle).  This  extended  envelope  then  undergoes  a  peculiar 
development;  pushed  gradually  against  the  vitelline  mem- 
brane, it  is  duplicated  (Fig.  137,  2,  and  Fig.  139,  2,  dotted 
lines),  induces  absorption  of  the  latter,  is  substituted  for 
it,  and  thus  becomes  the  most  external  fold  of  the  egg\ 
in  its  turn  it  presents  little  protuberances,  and  so  forms  the 
secondary  chorion  (Fig.  140,  2').  This  second  chorion  is  no 
more  vascular  than  the  first;  up  to  this  time  the  foetus 
obtains  its  nutrition  from  the  maternal  organism  only  by 
imbibition,  or  receives  it  by  means  of  the  nutritive  provision 
of  the  yellow  (umbilical  vesicle).  But  the  development  of 
the  second  chorion  allows  the  establishment  of  a  definite 
centre  of  exchange  between  the  mother  and  embryo,  by  the 
formation  of  the  allanto'is,  one  part  of  which  will  form  the 
placenta. 

Thirdly,  the  allantois  is  a  pouch  or  protuberance  from  the 
inferior  part  of  the  intestinal  canal  (see  p.  139,  a/,  and  Fig. 
124,  p.  458).  When  this  pouch  appears  (Fig.  139,  aQ,  the 
amniotic  cavity  is  so  much  developed  that  it  surrounds  the 
entire  foetus,  and  encloses  the  pedicle  of  the  umbilical  vesicle, 


Fig.  140.  —  Umbilical  vesicle  and  development  of  the  allantoTs.* 

in  such  a  way  as  to  form  a  cord  by  which  the  foetus  is  sus- 
pended in  the  waters  of  the  amnios.  The  allantoid  protu- 
berance insinuates  itself  in  this  cord  (Fig.  140,  o/),  pushes 
through  and  places  itself  by  the  side  of  the  pedicle  of  the  um- 
bilical vesicle  (omphalo-mesenteric  duct),  and  then  comes  in 

♦  o,  Umbilical  vesicle,    a/,  Allantois.    a,  Cavity  of  the  amnios.    2',  Second 
choriou. 


504 


URO-GENITAL  SYSTEM. 


contact  with  the  deep-seated  surface  of  the  second  chorion, 
whicli  we  have  just  studied.  It  extends  over  and  substitutes 
itself  for  this  surface,  or,  at  any  rate,  penetrates  the  whole 


Pig.  141.  —  Development  of  the  allantois  and  tliird  chorion.* 


Fig.  142.— TUrd  chorion  or  vascular  chorion.t 

of  the  outside  of  the  Q^g  between  the  external  surface  of  the 
amnios  and  the  internal  surface  of  the  chorion  (Fig.  141,  13, 


*  o.  Umbilical  vessel  in  process  of  atrophy,  al,  Allantois.  13, 14,  Allantois 
extending  upon  the  internal  surface  of  the  second  chorion,  a,  Cavity  of  tlie 
amnion.    (Ktilliker,  "  Entwickelimgsgeschichte." ) 

t  a,  Amniotic  cavity,  well  developed,  o,  Umbilical  vesicle,  almost  com- 
pletely atrophied,  al,  AUantoId  vesicle,  properly  speaking.  15,  Its  vascular 
villi  completely  developed,  and  forming  the  third  chorion  or  vascular  chorion 
around  the  c^q  (see  explanation  of  Fig.  139  for  the  distinction  of  the  dark,  in- 
terrupted, and  dotted  lines).    (Kolliker,  "Entwickelungsgeschichte.") 


J 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      505 

14).  In  fact,  the  allantois,  primarily  vesicular,  spreads  into 
a  membrane  which  is  filled  with  villi,  which  latter  penetrate 
into  the  villi  of  the  second  chorion.  These  villi  of  the 
allantois  are  vascular,  and,  uniting  with  the  second  chorion 
they  form  an  enveloping  membrane  of  the  ovum,  which  defi- 
nitely replaces  the  second  chorion  (Fig.  143,  15),  and  differs 
from  the  latter  by  the  fact  that  its  membrane  is  vascular  and 
consequently  capable  of  directly  seeking  by  means  of  a 
regular  circulation  (second  circulation)  the  nutritive  elements 
supplied  by  the  mother,  and  strained  through  the  decidua, 
whose  formation  we  have  previously  studied  (see  Fig.  136). 
This  is  what  authors  call  the  third  or  vascular  chorion^  or 
that  membrane  formed  by  the  allantois,  which  afterwards 
becomes  the  most  external  of  the  proper  envelopes  of  the 
G^^^  and  which  forms  a  covering  for  the  remainder  of  the 
second  chorion  (Fig.  142,  15). 

But  these  formations  from  the  allantois  last  only  for  a 
short  time,  especially  in  the  human  foetus.  We  have  already 
learned  that  those  portions  of  the  allantois  Avhich  are  nearest 
the  fcetus  form  successively  the  bladder  and  urachus  (see  p. 
460) ;  the  other  portion,  from  which  the  third  chorion  is 
formed  (Fig.  142,  15),  is  provided  with  vessels  only  on  the 
parts  which  correspond  to  the  meynhrana  decidua  serotina 
(see  p.  497)  ;  everywhere  else  the  vascular  loops  of  the 
villi  undergo  atrophy,  and  become  the  seat  of  no^ further 
transformations  at  these  points  until  the  bkth  of  the  foetus 
(Fig.  143). 

The  envelopes  of  the  perfected  ovum  are  everywhere  the 
same  except  at  the  placental  attachments.  Proceeding  from 
the  outside  towards  the  interior  are  (Fig.  143)  :  first,  the 
decidua,  or  rather  deciduae  (see  p.  497),  since,  by  the 
acquired  developments  of  the  Qgg^  the  decidua  reflexa  is 
in  contact  with  the  maternal  decidua,  or  decidua  vera  (c, 
Fig.  136),  and  since  these  two  membranes  are  not  distinct 
from  each  other;  however,  they  may  be  separated  by  a 
dissection,  and  often  a  certain  amount  of  fluid  may  be  found 
between  the  membranes  {hydroperion  of  Velpeau)  (21  and 
23,  Fig.  143)  ;  next  comes  the  chorion  (fusion  of  second  and 
third  chorions,  19,  Fig.  144),  the  cells  and  villi  of  which,  after 
the  disappearance  of  the  vessels,  are  united  and  fused  in  such 
a  manner  as  to  form  a  homogeneous  membrane,  which  is 
more  or  less  granular  and  interspersed  with  nuclei  (Robin)  ; 
third,  a  layer  of  irregular  cells^  which  are  the  remains  of  the 
allantoid  body,  is  formed  below  the  chorion ;  these  have  a  stel- 


506 


URO-GENITAL  SYSTEM. 


late  form,  placed  among  a  feT\'  connective  fibres,  and  float  in  a 
semi-fluid  substance  ;  this  is  the  magma  reticulata  of  authoi-s; 
lastly,  comes  the  amnion  which  forms  the  amniotic  pouch  or 
dimHicylum^  and  contains  the  amniotic  fluid  (Fig.  143,  18). 
Tiie  structure  of  the  amniotic  membrane  recalls  that  of  the 


Fig.  143.— Envelope  of  the  perfected  ovum,  — placenta.* 

skin,  with  which  it  is  continuous  and  whose  origin  it  shares 
(external  fold  of  the  blastoderm)  ;  in  fact,  it  is  composed  of 
an  epithelial  layer  of  pavement  cells  and  a  sort  of  dermis, 
formed  of  cellular  tissue,  which  contains  some  smooth  muscu- 
lar elements. 

Placenta.,  Nutrition  of  the  Foetus,  —  The  essential  office  of 
the  allantois  consists  in  the  formation,  at  the  point  where  the 
villi  still  exist  and  which  also  have  an  exaggerated  develop- 
ment (at  the  decidua  serotina)^  the  principal  organ  for  the 
nutrition  of  the  foetus,  viz.,  the  placenta.  In  fact,  at  this 
place  the  villi  of  chorion  and  allantois  {chorio-allanZo'id  villi) 
are  developed,  spread  out  in  every  direction  {placenta  froih- 
dosum)y  and  ramify  in  the  membrana  serotina  (Fig.  143,  i^2), 


*  a,  Amniotic  cavity  (the  body  of  the  foetus  is  not  represented ;  at  16  the 
umbilical  cord,  cut  at  the  point  of  attachment  to  the  umbilicus  at  17).  o,  Ite- 
mains  of  the  umbilical  vesicle.  18,  Amnion.  19,  The  definite  chorion.  20,  Pla- 
cental foetus.  21,  Mucous  layer,  or  uterine  caduca.  22,  Materaal  placenta.  23, 
Foetal  caduca,  or  membrana  reflexa.    24,  Muscular  tissue  of  the  uterus. 


DEVELOPMENT  OF  TEE  FECUNDATED  EGG.      507 

which  here  undergoes  an  hypertrophy ;  it  is  moreover 
characterized  by  the  })resence  of  both  vascular  and  ramified 
villi.  These  villi  originating  on  either  membrane  are  joined 
together,  interlace,  and,  finally,  form  the  more  or  less  circular 
and  apparently  compact  cake,  which  becomes  the  centre  of 
exchange  between  the  maternal  and  foetal  organism  (Fig.  143, 
20). 


Fig.  144.  — Diagram  of  the  placental  vessels.* 

An  idea  of  the  method  of  interchange  between  the  mother 
and  foetus  is  represented  by  a  diagram  in  Fig.  144.  The 
foetus  receives  and  rejects  the  nutrient  materials  by  means  of 
an  osmotic  interchange  through  the  capillaries  of  each  villus ; 
this  constitutes  nutrition  and  respiration. 

The  foetal  respiration  is  effected  by  means  of  the  placenta ; 
we  have  already  spoken  of  this  form  of  respiration  (see  p. 
324)*  The  necessity  of  placental  respiration  is,  moreover, 
supported  by  the  serious  accidents  which  result  from  suppres- 
sion of  the  placental  functions.  When  the  cir<}ulation  of  the 
cord  which  unites  the  placenta  to  the  foetus  {^qq  foetal  circu- 
lation)  is  interrupted,  the  foetus  perishes,  not  so  much  through 
want  of  nourishment,  as  from  a  true  asphyxia ;  at  birth  pulsa- 
tions in  the  cord  cease  only  when  the  infant  respires  through 
the  lungs,  because  then  the  new  method  of  respiration 
definitely  replaces  that  which  has  been  accomplished  by  the 
utero-placental  connection. 

The  nutrition  of  the  foetus  during  the  placental  portion  of 
its  life  consists  of  an  interchange  of  materials  between  the  foetal 
and  the  maternal  blood  through  the  placenta.  Moreover, 
the  relations  which  combine  both  nutrition  and  respiration 
are  much  simpler  in  the  foetus ;  the  adult  consumes  materi- 
als and  transforms  them  into  work  (see  Mechanical  equi- 
valent of  heat^  p.  78)  or  heat.     The  foetus  has  to  perform  no 

*  1,  Uterus.  2,  Intermediate  tissue.  3,  Placenta  (membrana  reflexa  seu 
caduca  serotina),  where  the  maternal  and  foetal  vessels  raiuify.  (Chailly- 
Honord.) 


508  URO-GENITAL  SYSTEM. 

work  and  expends  no  force ;  it  lias  not  even  to  produce 
heat,  it  receives  that  from  the  mother.  It  takes  alimentary- 
materials  only  for  the  building  of  tissues  and  the  devel- 
opment of  organs ;  consequently  the  difference  in  the  char- 
acter of  its  venous  and  arterial  blood  is  not  very  great, 
and  by  no  means  the  same  as  in  the  arterial  and  venous 
blood  ot  adult  life.  However,  oxidation,  no  matter  how 
feeble  it  may  be,  is  produced  in  the  embryo ;  thus,  the  heart 
performs  its  work  and  must  occasion  products  of  combustion ; 
moreover,  every  formation  of  tissue  is  accompanied  by  phe- 
nomena of  combustion,  which  should  give  rise  to  excremen- 
titial  products.  These  products  are  eliminated  principally  by 
the  liver  and  urinary  organs  (first  the  Wolffian  body  and 
then  the  kidneys)  ;  the  liver  is  also  very  much  developed  in 
the  embryo,  and  up  to  a  certain  point  it  may  replace  the 
lung  as  an  organ  for  the  excretion  of  organic  waste.  A 
certain  amount  of  urea  is  also  contained  in  the  bladder  of 
the  embryo,  which  is  thrown  off  into  the  amniotic  cavity. 
Consequently,  the  amniotic  fluid  contains  at  the  close  of  the 
embryonic  life  a  large  number  of  excrementitial  products, 
because  in  addition  to  the  urine  there  are  products  resulting 
from  the  desquamation  of  the  skin. 

II.  Development  of  the  tody  of  the  embryo. 

If  we  bear  in  mind  what  has  preceded  in  regard  to  the 
formation  of  the  umbilical  vesicle  (pp.  600  and  603)  we  shall 
also  understand  how  this  vesicle,  in  consequence  of  a  peculiar 
strangulation,  is  separated  from  the  common  blastodermic 
vesicle  (p.  687) ;  the  borders  of  the  germinal  space  or  area,  as 
well  as  its  cephalic  and  caudal  extremities  or  hoods,  drawn 
along  by  this  strangulation  or  constriction,  form  by  their 
curvatures  the  sides  as  well  as  the  cephalic  and  caudal  hoods 
(Fig.  137,  139,  140),  which  unite  and  form  a  cavity.  This 
cavity  might  be  likened  to  the  hollow  or  interior  of  a  slipper, 
and  communicates  with  that  of  the  umbilical  vesicle,  as  we 
have  before  stated  (Fig.  139,  p.  601).  This  is  \\iq  primary 
cavity  of  the  embryo^  or  rather  its  intestinal  cavity  (Fig. 
137,  12).  To  complete  this  rough  sketch  of  embryology  we 
will  proceed  to  the  consideration  of  the  two  grand  systems, 
the  nervous  system,  and  that  of  the  circulation. 

a.  Central  Nervous  System.  —  As  soon  as  the  germinal 
space  or  area  has  assumed  the  form  of  an  elongated  spot 
(like  the  sole  of  a  slipper)  a  central  longitudinal  line,  called 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      509 


the  primitive  groove,  appears;  this  serves  as  the  point 
of  origin  of  the  central  nervous  system  (spinal  cord  and 
cncephalon).  In  fact,  this  line  is  simply  a  groove  (Fig.  145) 
bounded  by  two  longitudinal  ridges  of  the  external  layer  or 
fold  {epihlast)  of  the  blastoderm.  These  two  ridges  (medul- 
lary folds.  Fig.  145,  3)  extend  backwards  and,  by  their 
union,  surround  the  medullary  canal.  This  canal  is  repre- 
sented in  the  adult  by  the  central  canal  of  the  spinal  cord 
with  the  fourth  ventricle  and  the  ventricles  of  the  brain  (and 
the  aqueduct  of  Sylvius).  The  incomplete  closure  of  this 
medullary  groove  results  in  the  formation  of  the  fourth  ven- 
tricle. It  is  generally  admitted  at 
the  present  time  that  the  external 
layer  of  the  blastoderm  {epiblast) 
forms  only  the  epithelium  of  the 
central  canal  of  the  spinal  cord 
(and  cerebral  ventricles,  vibratile 
epithelium,  see  p.  190),  and  that  the  ^ 
nerve  elements  originate  in  a  part  /; 
of  the  middle  layer  (mesohlast)  sub- 
jacent to  this  epithelium.  This  view 
is  confirmed  by  the  fact  that  every-  3 
where  else  the  nerve  elements  are  ^ 
formed  at  the  expense  of  the  inter- 
mediate layer  (mesoblast).  c 

The  upper  portion  of  the  medul- 
lary or  neural  canal  forms  the  ence- 
phalic substance ;  this  part  swells 
out  into  three  vesicles  (cerebral 
vesicles  or  cells)  which  are  respec- 
tively named  in  order,  from  front  to  ^^s- 1*5. 
back :  the  anterior  cerebral,  the  mid- 
die  cerebral,  and  the  posteiior  cerebral  cells,  or  the  first, 
second,  and  third  cerebral  vesicles.  The  anterior  or  first 
cerebral  cell  or  vesicle  is  again  divided  ii:to  two  portions,  the 
most  anterior  of  which  (anterior  of  the  brain),  overlaying  the 
second,  forms  the  cerebral  hemispheres  and  corpus  callosum, 
and  the  posterior  (intermediate  portion  of  the  brain)  forms 
the  thalami  optici  and  the  third  ventricle  (continuation  of 
the   medullary  canal)  :    2.   The  middle  or  second  cerebral 

*  1,  Medullary  groove.  2,  Inferior  enlargement  of  the  medullary  groove 
(rhomboid  sinus).  3,  Crests  or  medullary  folds  (laminae  dorsales).  5,  Middle 
and  external  folds  of  the  blastoderm.    6,  Inner  fold  of  the  blastoderm  (Bischoff). 


'^^^ipiifii 


Origin  of  the  nervous 
system.* 


510  URO-GENITAL  SYSTEM. 

vesicle  is  not  divided  (middle  portion  of  the  brain)  and 
forma  the  region  of  the  corpora  quadrigemina  with  the 
aqueduct  of  Sylvius  (continuation  of  the  medullary  canal); 
3.  The  posterior  or  third  cerebral  vesicle  divides,  like  the  first, 
into  two  portions;  one  of  which,  that  nearest  to  the  middle 
part  of  the  brain,  will  form  the  protuberance,  or  medulla 
oblongata,  and  the  cerebellum  (posterior  part  of  the  brain)  ; 
the  other  of  these  divisions,  a  direct  continuation  of  the 
spinal  cord,  will  form  the  rachidian  bulb  (medulla  oblongata, 
strictly  speaking) ;  this  is  the  point  in  which  the  medullary 
or  neural  canal  does  not  completely  close,  but  persists  in  its 
original  form  of  a  groove  and  constitutes  the  floor  of  the 
fourth  ventricle. 

Tiie  peripheral  nerves  are  formed  in  their  proper  place  at 
the  expense  of  the  middle  layer  (mesoblast)  of  the  blastoderm. 
The  o[)tic  nerve  and  retina  form  an  exception  and  are  repre- 
sented by  a  diverticulum  of  the  encephalic  substance  (see  p. 
425,  Fig.  113.) 

The  ganglia  of  the  great  sympathetic  are  also  formed  in 
their  proper  places,  independently  of  the  cerebro-spinal  sub- 
stance, and  fi-om  the  middle  layer  (mesoblast)  of  the  blasto- 
derm, as  we  have  already  learned,  in  treating  of  the  semi- 
lunar ganglia  of  the  abdominal  portion  of  the  sympathetic 
system  (see  p.  277). 

b.  Circulation  in  the  Embryo.  —  The  circulation  of  the 
embryo  depends  upon  its  method  of  nutrition.  As  we  have 
already  learned,  this  nutrition  of  the  embryo  may  be  effected 
in  three  different  ways  :  First,  by  the  simple  and  direct  assim- 
ilation of  the  albuminous  substance  in  which  the  ovum  is 
immersed ;  no  system  of  circulation  is  required  for  this 
simple  form  of  imbibition.  Second,  by  an  assimilation  of  the 
contents  of  the  umbilical  vesicle ;  these  contents  are  conveyed 
to  the  embryo  by  a  peculiar  system  which  forms  the  primary 
or  omphalo-mesenteric  circulation  (sometimes  written  om- 
phalo-mesaraic).  Third,  by  an  interchange  with  the  mater- 
nal blood  through  the  placenta ;  this  method  of  nutrition  is 
fulfilled  by  the  secondary  or  placental  circulatioii. 

1.  The  system  for  the  primary  circulation  commences 
with  the  formation  of  the  heart ;  this  organ  is  at  first  repre- 
sented by  a  cylinder  of  embryonic  globules ;  soon  the  sur- 
rounding globules  become  organized  into  muscular  fibres, 
whilst  those  at  the  centre  undergo  a  partial  dissolution  and 
form  the  first  blood.    Simultaneously  the  heart,  which  at  first 


DEVELOPMENT  OF   THE  FECUNDATED  EGG.      511 

Mas  longitiidinnl,  now  assumes  the  form  of  the  letter  S  (Fig. 
14G,  4),  and  coramcnces  to  contract  and  propel  the  blood  into 
the  peripheral  vessels. 

riiL'se  peripheral  vessels,  as  we  have  already  said,  are 
formed  in  their  proper  places  and  consist,  at  the  first,  of  two 
aortic  arches,  which  are  offshoots  from  the  anterior  extremity- 


rig.  146.  —Primary  circulation.* 

of  the  cardiac  tube.  These  curve  around  and  below  the 
cephalic  hood  {anterior  vertebral  arteries).,  unite  in  a  single 
trunk  {aorta)  at  the  median  portion  of  the  vertebral  column, 
and  again  divide,  descendiiig  towards  the  caudal  exti'emity 
of  the   embryo   by  two  branches,   the  posterior  vertebral; 

*  (Icriiuiijil  art'a  of  an  embryo;  the  ventral  surface  of  the  embryo  is  pre- 
sented. I,  Terminal  sinus.  2,  Omphalo-mesenteric  vein.  3,  Its  posttrinr 
branch.  4,  Heart  in  the  form  of  an  S.  5,  Primitive  aorta,  or  posterior  vertebral 
arteries.  (J,  Omphalo-mesenteric  arteries.  (lUschoff,  "  Devel<»ppement  »le 
rilomme,"  p.  Ixiv.) 


512  URO-GENITAL  SYSTEM. 

these  will  form  at  a  later  period,  following  a  posterior  direc- 
tion, the  two  iliac  arteries.  Numerous  arterial  branches, 
the  most  remarkable  of  which  on  account  of  size  are  those 
which  go  to  the  intestine  and  umbilical  vesicle  (Fig.  146,  5), 
are  sent  off  from  the  posterior  vertebral  arteries,  and  distrib- 
ute blood  to  the  tissues  of  the  embryo ;  these  two  omphalo- 
mesenteric arteries  are  most  essential  to  the  primary  circula- 
tion (146,  6).  The  blood  goes  through  them  to  the  walls  of 
the  umbilical  vesicle,  and  percolating  there  in  a  rich  network, 
which  occupies  only  a  portion  of  this  vesicle  {area  vasculosa^ 
Fig.  146),  it  is  charged  with  the  nutritive  elements  of  the  yolk, 
and  is  afterwards  launched  into  a  sinus,  which  occupies  the 
outside  of  the  area  vasculosa  {terminal  sinus^  sinus  venosus. 
Fig.  146,  1) ;  the  blood  then  returns  through  two  veins 
(omphalo-mesenteric)  to  the  posterior  extremity  of  the  car- 
diac cylinder  (Fig.  146,  2,  3).  This  primary  circulation  lasts 
but  a  short  time  in  the  human  embryo,  as  the  functions  of 
the  umbilical  vesicle  soon  cease  and  the  vesicle  undergoes 
atrophy  (see  p.  502)  ;  so  also  at  this  period  the  corresjionding 
portion  of  the  omphalo-mesenteric  vessels  undergo  the  same 
fate,  the  arteries  being  reduced  to  one  mesenteric  artery,  the 
veins  to  one  mesenteric  vein,  and  thus  form  the  future  vena 
portCB. 

2.  The  remainder  of  the  primary  circulation,  thus  modified, 
anvl  with  the  addition  of  new  vessels,  then  forms  the  second- 
ary ov  placental  circulation.  We  will  consider  the  formation 
of  the  organs  of  this  new  system,  by  commencing  with  the 
placenta,  and  the  course  of  the  blood  towards  the  heart  by 
the  venous  system,  and  its  return  from  the  heart  of  the  foetus 
to  the  placenta  tlirough  the  arterial  system. 

a.  Placental  Venous  System.  —  The  blood  that  become^ 
charged  in  the  placenta  with  constructive  elements  received 
from  the  blood  of  the  mother  (see  p.  506)  goes  to  the  body 
of  the  Ibetus  by  two  veins  which  are  developed  on  the  pedi- 
cle of  the  allantois ;  these  veins  pass  into  the  embryo  with 
the  umbilicus,  whence  their  name  of  umbilical  veins.  One 
of  these  vessels  immediately  becomes  atrophied,  and  only 
one  umbilical  vein  then  remains,  which  unites  with  the 
posterior  extremity  of  the  heart  to  form  the  central  end  of 
the  mesenteric  vein;  so  that  this  central  end  which  was 
primarily  the  omphalo-mesenteric  {pmphalo-mesaraic)  trunk, 
afterwards  the  trunk  of  the  mesenteric  vein,  now  repre- 
sents the  common  trunk  of  the  umbilical  and  mesenteric 
veins  (Fig.  149,  1 ;  yet  the  transformations  do  not  rest  here. 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      513 

A  protuberance  is  formed  upon  this  common  trunk  which 
serves  for  a  vascular  blood  gland^  or  the  Uver  {glycogenic 
])ortion  of  the  liver,  see  pp.  232  and  265)  ;  so  soon  as  the 
liver  is  formed  around  the  common  trunk  of  the  umbilical 
and  mesenteric  veins,  each  of  these  veins  sends  into  this 
glandular  protuberance,  or  rather  pouch,  vascular  ramifica- 
tions ;  those  which  come  from  the  mesenteric  veins  form  the 
afferent  hepatic  veins,  and  those  which  come  from  the  com- 
mon trunk  form  the  efferent  hepatic  veins.    In  this  way, 


Fig.  147.— Diagram  of  the  development  of  the  ompbalo-mesenteric,  nmbllical, 
and  portal  veins.* 

and  as  more  clearly  indicated  in  the  Fig.  147  (B),  the  mesen- 
.^eric  vein  and  its  afferent  hepatic  veins  form  the  portal  sys- 
tem, whose  veins  ramify  in  the  liver  and  whose  subsequent 
union  comprises  the  efferent  hepatic  veins;  finally,  these 
latter  conduct  to  the  common  and  free  trunk  beyond  the 


•  A.  Period  corresponding  with  the  close  of  the  primary  and  commencement 
of  the  second  circulation.  —  1,  Common  trunk  of  the  omphalo-mesenteric  veins. 
2,  Right  omphalo-mesenteric  vein.  3,  The  left.  4,  Common  trunk  of  the  um- 
bilical veins  in  process  of  formation.  5,  The  right  umbilical  vein.  6,  The 
left. 

B.  Formation  of  the  Uver. — 1,  Permanent  mesenteric  vein  (future  portal 
vein).  2,  3,  Representing  the  place  of  the  atrophied  omphalo-mesenteric  veins. 
5,  Right  umbilical  vein  undergoing  a  process  of  atrophy.  6,  Permanent  mnbiii- 
cal  vein.  7,  Canal  of  Cuvicr  (ductus  Cuvieri).  8,  Anterior  or  superior  cardinal 
veins.  9,  Posterior  or  inferior  cardinal  veins,  or  jugular  veins.  10,  Liver,  wnth. 
the  afferent  and  efferent  veins. 

C.  Formation  if  the  cena porta  and  canalis  Arantii  sett  ductus  venosus  (per- 
fected state  of  the  placental  circulation).  1,  Remains  of  the  omphalo-mesenteric 
(omphalo-mesaraic)  vein.  13,  Mesenteric  vein  (portal  vein).  6,  Umbilical  vein. 
4,  Ductus  venosus  se7t  canalis  Arantii.  12,  Afferent  hepatic  veins.  11,  Efferent 
hepatic  veins.    (Kolliker.) 

sa 


514 


URO-GENITAL  SYSTEM. 


liver.     This  portion  of  the  old  trunk  afterwards  forms  the 
upper  part  of  the  inferior  vena  cava,  whose  lower  portion  ig 


Fig.  148.  —  Venous  system  of  the        Fig.  149.  —  Formation  of  tlie  true  or  per- 
embryo.*  manent  venous  system. t 

*  1^  Duct  i.i  Cuvier.  2,  Place  where  all  the  veins  unite  and  pour  their  con- 
tents into  the  inferior  extremity  of  the  heart  (future  auricle).  3,  Anterir^r 
car'Jinal  vein.  6,  Umbilical  vein.  7,  Tlie  same  vein  near  the  liver  (which  is 
i:ot  in  the  plate,  neither  the  afferent  and  efferent  hepatic  veins).  8,  Omphalo- 
mesenteric vein.  9,  Inferior  vena  cava.  12,  i'osterior  cardinal  veins.  KoUiker, 
"  Entwickelunijsgcschichte.") 

t  A.  Period  of  forvitxt ion.  —  1,  Left  superior  vena  cava.  2,  Eight  superior 
vena  cava.  3,  Inferior  A-ena  cava.  4,  5,  Inferior  cardinal  veins  (future  azygos). 
7,  Anastomosis  between  the  two  autcrior  cardinal  veins,  future  left  brachio- 
cephalic trunk.    8,  9,  10,  Future  jugular  and  subclavian  veins. 

B.  Permanent  venous  trunks  (as  in  the  adult).  —  These  vessels  (as  in  the  Fig. 
A)  are  represented  as  if  looking  at  the  posterior  portion  of  the  body.  1,  Oblit- 
erated left  superior  vena  cava.  6,  Kiglit  vena  innominata.  7,  Left  vena 
innomiiiata.  8,  Sul)clavian.  13,  Trunk  of  the  hcmi-azygos,  18,  Left  superior 
intercostal.     19,  20,  Superior  and  infei-ior  portions  of  the  left  azygos. 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      515 

completed  by  a  development  of  a  trunk  which  collects  the 
l)lood  tliat  comes  from  the  undeveloped  lower  limbs.  The 
ductus  venosus  (canalis  Arantii)  and  the  sinus  venosus  are 
formed  of  that  portion  of  the  umbilical  and  mesenteric  veins, 
which  lies  between  the  confluence  of  the  aflerent  hepatic  and 
efferent  hepatic  veins  (Fig.  147,  B  and  C,  4). 

We  will  not  insist  upon  the  ulterior  results  of  this 
arrangement,  which  is  one  of  the  most  complicated  points 
in  the  anatomy  of  the  liver.  It  is  only  necessary  to  under- 
ftand  that  the  umbilical  vein,  when  it  arrives  at  the  liver, 
pours  a  part  of  its  contents  into  the  portal  vein  (into  the 
left  portion  of  the  portal  vein),  and  conveys  another  portion 
through  the  ductus  venosus  directly  into  the  lower  vena 
cava,  and  thence  to  the  heart. 

The  veins  which  collect  the  blood  from  the  body  of  the 
embryo  (anterior,  or  superior,  and  posterior,  or  inferior,  cardi- 
nal, and  lower  vena  cava,  see  Fig.  148)  empty  their  contents 
simultaneously  and  on  each  side,  into  a  common  duct  (canalis 
Cuvieri).  But  this  arrangement  does  not  long  continue  ;  for 
soon  the  posterior,  or  inferior,  cardinal  veins  become  partially 
atroj^hied,  and  the  only  trace  of  their  existence  is  found  in 
the  azygos  veins  (large  and  small  azygos,  see  Fig.  149,  B). 
Between  the  anterior  cardinal  veins  a  transverse  duct  (left 
brachio-cephalic,  7,  A  and  B,  Fig.  149)  is  formed,  simulta- 
neously with  the  atrophy  of  the  left  Cuverian  duct.  On  the 
other  hand,  the  right  duct  of  Cuvier  persists  and  becomes 
the  superior  vena  cava  (Fig.  149,  A,  6).  We  thus  understand 
the  arrangement  of  the  right  azygos  vein  (large  azygos) 
which  in  the  adult  conducts  the  blood  into  the  superior  vena 
cava,  since  it  represents  the  central  end  of  the  right  posterior 
cardinal  vein ;  as  well  as  the  arrangement  of  the  right  brachio- 
cephalic trunk,  which  represents  the  central  end  of  the  right 
superior  cardinal  vein.  At  this  period  of  embryonic  existence 
the  inferior  and  superior  venaB  cava)  empty  their  contents  into 
the  heart  by  a  common  trunk,  while  at  a  later  period  of  its 
existence  this  common  trunk  gradually  becomes  a  portion  of 
the  wall  of  the  auricular  cavity ;  so  that,  after  a  wliile,  the 
two  venae  cavae  separately  connect  with  the  auricle  (as  in  the 
adult)  at  a  little  distance  from  each  other. 

b.  Heart.  —  The  central  organ  of  circulation,  at  first  repre- 
sented in  the  form  of  a  simple  and  cylindrical  tube,  after- 
wards resembling  the  letter  S  (Fig.  146),  becomes  divided  by 
means  of  increasing  constrictions  into  three  cavities,  viz.,  the 
auricular,   ventricular,    and    arterial    (aortic   bulb   or   sinus, 


516  URO-GENJTAL  SYSTEM. 

bulbus  arteriosus).  The  curvature  of  the  heart  gradually 
increases  in  such  a  manner  that  the  ventricle,  which  at  first 
was  placed  above,  turns  downwards  and  forwards,  and  the 
auricle  upwards  and  backwards.  Simultaneously  Avith  the 
establishment  of  the  placental  circulation,  a  median  partition, 
or  septum,  originates  at  the  apex  of  the  ventricle,  whose 
extension  finally  divides  the  single  ventricular  cavity  into  two 
cavities,  called  the  right  and  left  ventricle.  A  partition  is 
also  formed  in  the  large  sinus  of  the  aorta  (bulbus  arteriosus), 
the  latter  having  assumed  a  spiral  form ;  this  partition  divides 
the  sinus  into  two  ducts  which  are  twisted  on  their  axes ; 
one  of  these  ducts  communicates  with  the  right  ventricle 
(the  origin  of  the  pulmonary  artery)  and  the  other  with  the 
left  ventricle,  which  latter  becomes  the  origin  of  the  aorta. 

The  auricular  cavity  is  also  gradually  divided  into  a  right 
and  a  left  auricle,  by  a  septum  which  originates  at  the  auriculo- 
-ventricular  region.  Yet  during  the  remainder  of  the  fcEtal 
existence,  this  incomplete  partition  or  septum  contains  an 
opening  (foramen  Botalis  seu  ovale)  which  allows  of  a  com- 
munication between  the  two  auricles.  The  relations  of  this 
inter-auricular  opening,  with  the  mouths  of  the  venae  cavae 
in  the  right  auricle,  form  a  characteristic  feature  of  the  placen- 
tary  circulation.  The  mouth,  or  opening,  of  the  inferior  vena 
cava  is  provided  with  the  Eustachian  valve ;  this  valve  is 
largely  developed  at  this  period,  and  is  so  arranged  that  the 
blood  which  comes  from  the  inferior  vena  cava  can  only  go 
through  the  postero-inferior  portion  of  the  right  auricle,  and 
is  directed  towards  the  inter-auricular  opening;  by  this 
means  the  blood  is  diverted  through  the  foramen  ovale  into 
the  left  auricle,  and  thence  into  the  left  ventricle,  etc.  (see 
farther  on).  On  the  other  hand,  the  blood  which  comes 
from  the  superior  vena  cava,  there  being  no  such  valve  here, 
passes  from  the  right  auricle  (which  it  fills,  just  as  in  adult 
age)  by  the  auriculo-ventricular  orifice  directly  into  the  right 
ventricle,  etc.  (see  also  farther  on). 

c.  Arteries.  —  We  have  spoken  of  two  branches  that 
originate  from  the  anterior  extremity  of  the  cardiac  tube; 
these  soon  turn  towards  the  back  and  form  what  is  called  the 
first  pair  of  aortic  arches  (see  p.  511).  Soon  afterwards  two 
or  three  other  aortic  arches  are  successively  developed,  and 
are  behind  this  first  aortic  arch ;  these  also  unite  in  the  median 
trunk  of  the  descending  portion  of  the  aorta  (Fig.  150);  yet 
the  continuance  of  these  arches  is  only  very  transitory,  and 
most  of  them  are  soon  obliterated,  some  of  their  branches 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      617 

alone  remaining  to  form  the  large  and  permanent  branches 
of  the  circulation.  In  this  way  the  highest  of  these  arches 
becomes  the  right  brachio-cephalic  (arteria  innominata),  the 
carotid,  and   the   left   subclavian  arteries 

(Fig.  150,  5,  4)  ;   on  the   right   side   the ,i3y -,; 

second  arch  disappears,  but,  on  the  left,  it         I"    \|' p 

forms  the  arch  of  the  permanent  aorta  (3)  ;  ^^^^j^^,:^ 
the  third  sends  off  on  each  side  a  branch  i''^'^\\ 
which  ramifies  through  the  lung  of  the  -i^Wv?^] 
corresponding  side;  while,  on  the  right,  M*  vf\i^l 
the  portion  beyond  this  offshoot  becomes  *%  *  /A 
atrophied,  and  its  companion  on  the  left  %     // 

side  remains  and  furnishes  a  communica-  \J/ 

tion   between  the  pulmonary  artery  and  // 

the  arch  of  the  aorta;  this  is  called  the  Fig.  iso.— Aortic  arches 
ductus  arteriosus.     This  ductus  arteriosus      r"*}  fra^"*  "*  ^*^^' 
holds  the  same  relation  to  the  placental 
circulation  as  the  foramen  ovale  (of  Botal)  and  the  ductus 
venosus  (of  Aran  tins)  (see  p.  515). 

The  bulb  of  the  aorta,  moreover,  is  so  divided  that  the  part 
[of  its  cavity,  which  communicates  with  the  left  ventricle, 
is  a  continuation  of  the  remains  of  the  two  first  pairs  of 
aortic  arches  (carotids,  subclavians,  and  arch  of  the  perma- 
nent aorta)  ;  whilst  that  part  of  its  cavity,  which  communi- 
cates with  the  right  ventricle,  is  a  continuation  of  the 
remains  of  the  third  aortic  arch,  the  pulmonary  artery  (and 
the  ductus  arteriosus)  (Fig.  150,  1). 

If  we  pursue  the  arrangement  of  the  arterial  system  from 
centre  to  the  periphery,  we  shall  find  that  the  descending 
portion  of  the  aorta  gradually  elongates  (p.  512),  and  that 
the  two  posterior  vertebral  arteries  become  the  iliac  arteries  / 
from  these  latter  are  given  off  two,  relatively,  very  large 
branches,  which  are  called  the  umbilical  arteries  ;  these  fol- 
lowing the  pedicle  of  the  allantois,  and  entwining  around  the 
single  umbilical  vein  in  the  umbilical  cord,  convey  blood 
from  the  foetus  towards  the  placenta ;  at  this  point  the  blood 
is  distributed  in  the  capillaries  of  the  villi,  and  comes  into 

*  1,  Trunks  which  spring  from  each  ventricle  (bulbus  arteriosus  dividing 
into  the  origin  of  the  aorta  and  origin  of  the  puhnonary  artery ) ;  above,  live 
pairs  of  aoi'tic  arches  may  be  seen ;  the  highest  of  these  disappear ;  only  tlie 
three  which  are  nearest  the  heart  become  permanent  vessels,  and  represent  the 
eubclavian,  the  right,  and  the  left  carotid  arteries  5,  4.  3,  The  arch  of  the  aorta. 
2,  The  descending  portion  of  the  aorta ;  the  ductus  arteriosus,  which  has  only  a 
very  transitory  existence,  may  be  seen  at  the  junction  of  the  arch  of  the  aorta 
with  its  descending  portion. 


518 


URO-GENITAL  SYSTEM. 


those  relations  of  interchange  with  the  blood  of  the  mother 
ah-eady  spoken  of  (p.  507).  We  have  now  returned  to 
the  point  from  which  we  set  out,  and  have  successively  passed 
through  the  various  segments  of  the  circle  of  the  placental 
circulation.  We  are  now  prepared  to  review  in  a  brief 
space,  and  present  a  summary  of  the  method  by  which  tlio 
blood  moves  through  the  vessels,  from  the  foetus  to  the 
placenta,  and  from  the  placenta  to  the  foetus ;  also  how  this 
placental  circulation  mingles  with  the  circulation  in  the 
different  parts  of  the  embryo  (head,  limbs,  and  viscera). 

Summary.  —  The  blood  comes  from  the  placenta  through 
the  umbilical  vein  and  goes  to  the  lower  surface  of  the  liver, 
thence  it  is  returned  into  the  lower  vena  cava  by  two  differ- 
ent channels ;  a  portion  returns  directly  to  the  lower  vena 
cava  through  the  ductus  venosus  of  Arantius;  the  other 
portion  goes  through  the  left  branch  of  the  portal  vein,  is 
distributed  in  the  left  lobe  of  the  liver,  whence  it  flows 
through  the  corresponding  hepatic  veins  to  the  lower  vena 
cava ;  it  may  be  noticed  that  the  left  lobe  of  the  liver,  by 
this  arrangement,  receives  a  mixture  of  intestinal  venous 
blood  (portal  vein)  and  a  blood,  which  has  been  vivified  by  its 
passage  through  the  placenta  (umbilical  vein),  whilst  the 
right  lobe  receives  only  the  intestinal  blood.  This  explains 
the  increased  size  and  development  of  the  left  lobe ;  since 
the  preponderance  of  the  lobes  is  reversed  in  the  liver  of 
adult  age. 

The  blood  from  the  inferior  vena  cava  passes  into  the  right  \ 
auricle;  yet  it  apparently  only  skims  through  this  cavity 
without  being  mingled  with  the  blood  from  the  superior  vena 
cava.  In  fact  (see  p.  516),  the  blood  of  the  inferior  vena 
cava,  guided  by  the  Eustachian  valve,  passes  through  the 
foramen  ovale  into  the  left  auricle,  thence  into  the  left  ven- 
tricle, and  so  into  the  arch  of  the  aorta.  At  the  last- 
named  place  a  small  part  of  this  blood  is  taken  by  the 
descending  portion  of  the  aorta,  where  we  shall  presently 
find  it  mingling  with  the  blood  furnished  by  the  ductus 
arteriosus ;  the  larger  part  of  the  blood  received  into  the 
arch  of  the  aorta  traverses  the  brachio-cephalic  (innominate), 
the  carotid,  and  subclavian  trunks,  for  the  purpose  of  furnish- 
ing nutrition  for  the  head  and  arms.  Let  us  not  forcjet  that 
this  blood,  thus  supplied  to  the  upper  extremities  of  the 
embryo,  is  almost  wholly  arterial,  that  is  to  say,  has  been 
vivified  by  the  placental  haematosis,  with  scarcely  any  venous 
blood  (only  that  from  the  inferior  vena  cava  and  the  hepatioi 


DEVELOPMENT  OF  THE  FECUNDATED  EGG.      519 

veins).  Having  become  venous,  this  blood  from  the  head 
and  upper  extremities  returns  through  the  superior  vena 
cava  to  the  right  auricle,  thence  to  the  right  ventricle  (see  p. 
516)  and  the  pulmonary  artery.  Since  the  lung  at  this 
period  forms  a  compact  mass,  and  scarcely  permeable,  the 
blood  of  the  pulmonary  artery  passes  directly  into  the  duc- 
tus arteriosus,  and  thence  down  the  descending  portion  of 
the  aorta,  where  it  mingles  with  that  small  amount  of  arterial 
blood,  which  is  not  sent  from  the  arch  of  the  aorta  to  the 
lower  extremities  of  the  foetus.  Having  arrived  at  the 
primary  iliac  arteries,  a  large  amount  of  the  blood  is  diverted 
through  the  umbilical  arteries  for  the  purpose  of  undergoing 
haBuiatosis  in  the  placenta,  whilst  a  smaller  amount  continues 
on  its  course  through  the  iliacs,  in  order  to  nourish  the  pelvis 
and  lower  extremities  of  the  foetus. 

Respecting  the  character  of  the  blood,  which  the  different 
portions  of  the  body  of  the  embryo  receive,  it  maybe  noticed 
that  its  upper  part  receives  arterial,  mixed  with  a  small  quan- 
tity of  venous  blood ;  whilst  the  parts  below  the  umbilicus 
receive  venous,  mixed  with  a  small  quantity  of  arterial  blood. 
This  difference  corresponds  with  what  we  have  mentioned  in 
respect  to  the  two  lobes  of  the  liver,  and  explains  the  pre- 
ponderance of  size,  and  increased  development,  of  the  upper 
over  the  lower  part  of  the  body  of  the  embryo. 
.  This  placental  or  secondary  circulation^  with  its  mode  of 
nutrition  and  respiration  to  which  it  is  adapted,  continues 
imtil  the  birth  of  the  embryo.  At  this  latter  stage  the 
placental  circulation  ceases,  and  is  replaced  by  the  functions 
of  nutrition  and  respiration  which  we  have  already  studied  in 
the  adult.  The  disappearance  of  the  secondary  circulation 
follows  the  same  order  that  we  have  just  studied :  lirst,  the 
placenta,  which  is  thrown  oft'  after  the  expulsion  of  the 
Ibetus  (under  tlie  name  of  after-birth) ;  then  the  umbilical 
vein,  which  is  cut  and  obliterated  by  the  teeth  of  animals, 
or  by  direct  section  after  ligation  in  mankind.  That  portion 
of  this  vein,  which  goes  from  the  umbilicus  to  the  liver,  is 
also  obliterated  by  a  retraction  of  its  sides,  as  also  the  ductus 
venosus  of  Arantius;  these  vessels  are  replaced  by  the 
fibrous  ligaments  which  we  have  studied  in  descriptive 
anatomy.  The  Eustachian  valve  in  the  heart  undergoes 
atrophy,  the  foramen  ovale  is  obliterated,  and  the  two  auri- 
cles thenceforth  are  separated  ;  the  right  auricle  transmits  to 
the  right  ventricle  the  blood  from  the  inferior  vena  cava  as 
well  as  that  from  the  superior  vena  cava. 


520 


URO-GENITAL  SYSTEM. 


Moreover,  the  lung  becomes  permeable  and  the  ductus 
arteriosus  atrophied ;  the  blood  from  the  right  ventricle  goes 
directly  to  the  lungs.  Finally,  the  umbilical  arteries  are 
obliterated  by  hypertrophy  and  retraction  of  their  sides,  and 
are  represented  by  the  fibrous  ligaments  found  on  the  walls 
of  the  bladder ;  the  aorta  carries  the  blood  only  to  the  limbs, 
to  the  surface  of  the  body,  and  to  the  viscera;  the  two 
circles  of  the  permanent  circulation,  with  C(  mplote  inde- 
J)endence  of  each  other,  are  then  formed. 


APPENDIX. 


COMPABISON  OF  THE  THERMOIifETRIC  SCALES. 

The  following  rules  will  be  found  convenient  for  translating  the  degrees  of 
one  scale  into  those  of  another:  — 


1.  To  reduce  Centigrade  degrees  to 
those  of  Fahrenheit,  multiply  by  9,  and 
divide  by  5,  and  to  the  quotient  add  32 ; 
that  is,  — 


Cent.  X  9 


+  32  =  Fahr. 


2.  To  reduce  Fahrenheit's  degrees  to 
Centigrade :  — 

Fahr.  — 32x5 
9 


Cent. 


Fahrenheit. 

Centignde. 

FahrenheiU 

Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

Centigrade. 

212 

100 

195 

90.5 

177.8 

81 

160 

71.1 

211 

99.4 

194 

90 

177 

80.5 

159.8 

71 

210.2 

99 

193 

89.4 

176 

80 

159 

70.5 

210 

98.9 

192.2 

89 

175 

79.4 

158 

70 

209.7 

98.7 

192 

88.8 

174.2 

79 

157 

09.4 

209 

98.3 

191.7 

88.7 

174 

78.8 

156.2 

69 

208.4 

98 

191 

88.3 

173.7 

78.7 

156 

68.9 

208 

97.8 

190.4 

88 

173 

78.3 

155.7 

68.7 

207.5 

97.5 

190 

87.8 

172.4 

78 

155 

68.3 

207 

97.2 

18D.5 

87.5 

172 

77.7 

154.4 

68 

206.6 

97 

189 

87.2 

171.5 

77.5 

154 

67.7 

206 

96.6 

188.6 

87 

171 

77.2 

153.5 

67.5 

205.2 

96.2 

188 

86.6 

170.6 

77 

153 

67.2 

205 

96.1 

187.2 

86.2 

170 

76.6 

152.6 

67 

204.8 

96 

187 

86.1 

109.2 

76.2 

152 

66.6 

204 

95.5 

186.8 

86 

169 

76.1 

151.2 

63.2 

203 

95 

183 

85.5 

168.8 

76 

151 

66.1 

202 

94.4 

185 

85 

108 

75.5 

150.8 

66 

201.2 

94 

184 

84.4 

167 

75 

150 

65.5 

201 

93.9 

183.2 

84 

166 

74.4 

149 

65 

200.7 

93.7 

183 

83.9 

1G5.2 

74 

148 

64.4 

200 

93.3 

182.7 

83.7 

165 

73.9 

147.2 

64 

199.4 

93 

182 

83.3 

164.7 

73.7 

147 

63.9 

199 

92.7 

181.4 

83 

164 

73.3 

146.7 

63.7 

198.5 

92.5 

181 

82.7 

163.4 

73 

146 

63.3 

198 

92.2 

180.5 

82.5 

163 

72.7 

145.4 

63 

197.6 

92 

180 

82.2 

162.5 

72.5 

145 

62.7 

197 

91.6 

179.6 

82 

1G2 

72.2 

144.5 

62.5 

196.2 

91.2 

17!^ 

81.6 

161.6 

72 

144 

62.2 

196 

91.1 

178.2 

81.2 

161 

71.6 

143.6 

02 

195.8 

91 

178 

81.1 

160.2 

71.2 

143 

61.6 

522 


APPENDIX. 


Fahrenheit. 

Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

Centigrade. 

Fahrenheit. 

Centigrade. 

142.2 

61.2 

115 

46.1 

87.8 

31 

60 

15.5 

142 

61.1 

114.8 

46 

87 

30.5 

59 

15 

141.8 

61 

114 

45.5 

83 

30 

58 

14.4 

141 

60.5 

113 

45 

85 

29.4 

57.2 

14 

140 

60 

112 

44.4 

84.2 

29 

57 

13.8 

139 

59.4 

111.2 

44 

84 

28.9 

56.7 

13.7 

138.2 

59 

111 

43.9 

83.7 

28.7 

56 

13.3 

138 

58.8 

110.7 

43.7 

83 

28.3 

55.4 

13 

137.7 

58.7 

110 

43.3 

82.4 

28 

55 

12.7 

137 

58.3 

109.4 

43 

82 

27.7 

54.5 

12.5 

136.4 

58 

109 

42.7 

81.5 

27.5 

54 

12.2 

136 

57.7 

108.5 

42.5 

81 

27.2 

53.6 

12 

135.5 

57.5 

108 

42.2 

80.6 

27 

53 

11.6 

135 

57.2 

107.6 

42 

80 

26.6 

52.2 

11.2 

134.6 

57 

107 

41.6 

79.2 

26.2 

52 

11.1 

134 

56.6 

106.2 

41.2 

79 

26.1 

61.8 

11 

133.2 

56.2 

106 

41.1 

78.8 

23 

51 

10.5 

133 

56.1 

105.8 

41 

78 

25.5 

50 

10 

132.8 

56 

105 

40.5 

77 

25 

49 

9.4 

132 

55.5 

104 

40 

76 

24.4 

48.2 

9 

131 

55 

103 

39.4 

75.2 

24 

48 

8.9 

130 

54.4 

102.2 

39 

75 

23.8 

47.7 

8.7 

129.2 

54 

102 

38.9 

74.7 

23.7 

47 

8.3 

129 

53.9 

101.7 

38.7 

74 

23.3 

46.4 

8 

128.7 

53.7 

101 

38.3 

73.4 

23 

46 

7.7 

128 

53.3 

100.4 

38 

73 

22.7 

45.5 

7.5 

127.4 

53 

100 

37.7 

72.5 

22.5 

45 

7.2 

127 

52.7 

99.5 

37.5 

72 

22.2 

44.6 

7 

12,3.5 

52.5 

99 

37.2 

71.6 

22 

44 

6.6 

12G 

52.2 

98.6 

37 

71 

21.6 

43.2 

6.2 

125.6 

52 

98 

36.6 

70.2 

21.2 

43 

6.1 

125 

51.6 

97.2 

36.2 

70 

21.1 

42.8 

6 

124.2 

51.2 

97 

36.1 

69.8 

21 

42 

5.5 

124 

51.1 

96.8 

36 

69 

20.5 

41 

5 

123.8 

51 

96 

35.5 

08 

20 

40 

4.4 

123 

50.5 

95 

35 

67 

19.4 

39.2 

4 

122 

50 

94 

34.4 

66.2 

19 

39 

3.9 

121 

49.4 

93.2 

34 

66 

18.8 

38.7 

3.7 

120.2 

49 

93 

33.9 

65.7 

18.7 

38 

3.3 

120 

48.9 

92.7 

33.7 

65 

18.3 

37.4 

3 

119.7 

48.7 

92 

33.3 

64.4 

18 

37 

2.7 

119 

48.3 

91.4 

33 

64 

17.7 

36.5 

2.5 

118.4 

48 

91 

32.7 

63.5 

17.5 

36 

2.2 

118 

47.7 

90.5 

32.5 

63 

17.2 

35.6 

2 

117.5 

47.5 

90 

32.2 

62.6 

17 

35 

1.6 

117 

47.2 

89.6 

32 

62 

16.6 

34.2 

1.2 

116.6 

47 

89 

31.6 

61.2 

16.2 

34 

1.1 

116 

46.6 

88.2 

31.2 

61 

16.1 

33.8 

1 

115.2 

46.2 

88 

31.1 

60.8 

16 

33 
32 

0.5 
0 

APPENDIX. 


523 


The  weight  of  the  Kilogramme  is  settled  hy  Act  of  Parliament  to  he  equal  to  15432.8487 
English  grains ;  but  according  to  the  U.  S.  Pharmacopeia  it  is  equal  to  15,434.023 
or  about  lb  ij  ^  viij. 
COMPARISON  OF  THE  METRICAL  WITH  THE  COMMON  MEASURES. 
By  De.  Warren  De  La  Rue. 


MEASURES  OF  LENGTH. 


Millimetre 

Centimetre 

Decimetre 

Metre    .    . 

Decametre 

Hectometre 

Kilometre 

Myriometre 


In  English  Feet 
=  12  Inches. 


0.0032809 

0.03280C0 

0.3280S99 

3.2808992 

32.8089920 

328.0899200 

3280.8992000 

32808.9920000 


In  English 

Yards 
=  3  Feet. 


In  EnglLsh 

Miles 

=  1,760  Yards. 


0.0010936 

0.0109363 

0.1093G33 

1093G331 

10.9363310 

109.3033100 

1093.6331000 

109363310000 


0.0000006 
0.0000062 
O.OO0CG21 
O.O0C6214 
0.0062138 
0.0621382 
0.6213824 
6.2138244 


1  Inch  =  2.539954   Centimetres. 
1  Foot  =  3.0479449  Decimetres. 


1  Yard  =  0.91438348  Metre. 

1  Mile  =  1.6093149   Kilometres. 


MEASURES  OF  SURFACE. 


1  Square  Inch  =  6.4513669      Square  Centimetres. 
1  Square  Foot  =  9.2899683      Square  Decimetres. 
1  Square  Yard  =  0.83609715    Square  Metre  or  Centaire. 
1  Acre  =  0.404671021  Hectare. 


MEASURES  OF  CAPACITY. 


In  Cubic 
Inches. 


In  Cubic  Ft. 

=  1,728 

Cubic  In. 


In  Pints 
=  34.65923 
Cubic  In. 


In  Gallons 
=  8  Pints 

=  277.27384 
Cubic  In. 


In  Bushels 
=  8  Gallons 
=  2218.19075 

Cubic  In. 


Millilitre,  or  cubic 
centimetre    .    .    . 

Centilitre,or  10  cubic 
centimetres .    .    . 

Decilitre,  or  100  cu- 
bic centimetres     . 

Litre,  or  cubic  deci- 
metre   

Decalitre,  or  centi- 
stere     

Hectolitre,  or  deci- 
Btere     

Kilolitre,  or  stere,  or 
cubic  metre  .    .    . 

Myriolitre,  or  deca- 
stere 


0.061027 

0.610271 

6.102705 

61.027052 

610.270515 

6102.705152 

61027.051519 

610270.515194 


0.0000353 
0.0003532 
0.0035317 
0.0353166 
0  3531658 
3.5316581 
35.3165807 
353.1658074 


0.001761 

0.017608 

0.176077 

1.760773 

17.607734 

176  077341 

1760  773414 

17607  734140 


0.00022010 

0.00220097 

0.02200967 

0.22009668 

2.20096677 

22  00966767 

220.09667675 

2200.96676750 


0.00CC27512 
0.00C275121 
0.002751208 
0.027512085 
0.27512C846 
2.751208459 
27.512084594 
275.120845937 


1  Cubic  Inch  =  16.3861759      Cubic  Centimetres. 
1  Cubic  Foot  =  28.3153119      Cubic  Decimetres. 
1  Gallon         =    4.513457969  Litres. 


524 


APPENDIX. 


MEASURES  OF  WEIGHT. 

In  English 
Gri^ins. 

In  Troy  Ounces 
=  480  Grains. 

In  Avoirdupois 

Lbs.  =  7,000 

Grains 

Milligcramme 

Centigramme 

Decigramme 

0.015432 

0 154323 

1.543235 

15.432349 

154.323488 

1543.234880 

15432.348800 

154323.488000 

0  000032 
0000322 
0.003215 
0.032151 
0.321507 
3.215073 
32.150727 
321.507267 

0.0000022 
0.0000220 
O.C002205 
0.0022046 
O.C220462 
0.2204G21 
2.2046213 
22.0462126 

Decagramme 

Hectogramme 

Kilogramme 

Myriogramme 

1  Grain      =    0.06479895  Gramme. 
1  Troy  Oz.=  31.103496      Grammes. 
I  Lb.Avd.=   0.45359265  Kilogramme. 

Note.  — These  tables  are  taken  from  "Lessons  in  Elementary  Chemistry, 
Koscoe,  B.A.,  F.R.S. 


by  H.E. 


INDEX. 


A. 

Absorption,  cutaneous  ....  370 

in  general   ....  254 

points  of      ....  273 

Accelerator  nerves  of  the  heart   .  167 

Accommodation,(of  the  eye)  .    .  428 

Acid  of  the  gastric  juice     .    .    .  239 

Adenoid  tissue 202 

Aglobulia,  or  Anaemia  ....  117 

Air,  complementary,  etc.   .    .    .  306 

of  reserve 

residual 

Albumen  of  the  blood    ....  127 

Albuminoids  (aliments)      .     .     .  210 

Albuminose 245 

Alcohol 212 

Aliments 207 

Allantois 503 

Alveoli,  pulmonary 282 

Amnion 502 

Anapnographia 306 

Angle,  facial 63 

Aponeuroses,  or  fasciae  ....  105 

Apophyses,  osseous 99 

Appendages  of  the  muscular  sys- 
tem       94 

Arantius,  canal  of 515 

Area,  germinal 508 

Arteries 152 

Articulate  speech 363 

Articulations 104 

Arytenoid  (cartilages)  ....  347 

(muscle) 348 

Asphyxia 328 

Astigmatism 434 

Auditory  nerve 412 

Auricle  (heart) 133 

Auriculo-v<entricular  system  .    .  134 


B. 

Rands  of  absorption,  blood 
reduced  of  Stokea    . 


119 
120 


Barytone,  voice  of  the   ....  859 

Basso,  voice  of  the 359 

Bile 260 

Bilifulvine 262 

Biline 262 

Bladder 472 

Blastema  {theory  of  the)     ...  9 

Blastoderm 17 

Blood,  in  general 110 

of  warm  and  cold  blooded 

animals 339 

buffycoat 126 

Bones 97 

Botal,  foramen  of 516 

Bradvfibrine 197 

Brain 34 

Breasts 379 

Bronchi 301 

Bruits  (or  sounds)  of  the  heart  138,  141 

muscular 86 

Brunner,  glands  of 232 

Bulb,  or  medulla  oblongata    .    .  49 

Butter 381 


Caduca 497 

Caffein 213 

Canals,  semicircular 412 

Capacity  of  the  lungs     ....    306 

Capillaries,  acid 120 

biliary 267 

lymphatic    ....    201 
vascular  ....  145, 159 

Carbonic  acid 129,  317 

Carbonic  oxide  (action  of)       120,  324 
(in  blood)  ...    120 

Cardiometer 144 

Camivora 215 

Caseine 210,  380 

Cavity  of  the  tympanum    .    .    .    416 
Cells  (or  vesicles)  cerebral  (foetus)    509 

contractile 67, 94 

mastoid 419 

Cellulose,  animal 211 


526 


INDEX, 


Centres,  moderator 54 

Centrifugal  and  centripetal  nerves  29,40 

Centres  cerebral 59 

nerve,  in  general    ...  32 

respiratory 335 

trophic 42 

vaso-motor 176 

Cerebellum 34 

Cerumen 416 

Cruminous  glands 416 

Change  of  voice,  age      ....  359 

Chemistry  of  respiration     .    .    .  317 

Chitine 211 

Chloride  of  sodium  (its  office  in 

alimentation) 209 

Cholesterine      ....     27, 262, 276 

Chorda  tj-mpani 405 

Chorions 502 

Choroid  coat 435 

Chyliferi 201,  256,  267 

Ch}  lilication 256 

Chyme 247 

Ciliary  processes 438 

Circle  of  dilfusion 428 

Cu'culation,  derivative  ....  102 

of  blood 131 

of  the  foetus      ...  510 

Cirrhosis  of  the  liver 265 

Clots    and    coagulation    of 

blood 125,  182 

Coca  (of  Peru) 213 

Cochlea 412 

Colic 253 

Colostrum 380 

Columns  of  spinal  cord  ....  43 

Combustion 72,  77,  322 

Concha  of  the  ear 414 

Cone,  lymphatic 196 

objective 427 

ocular 427 

pulmonary 287 

vascular 142,  152 

Consonants 361 

Contraction  of  the  arterioles    .     .  159 

of  the  muscles      .     .  84 

Cooling 377 

Cord,  vocal 348,  355 

Cornea 424 

Corneous  layer 366 

Corpora  quadrigemina  ....  59 

Coii)us  cailosum 61 

luteiim 492 

striatum 61 

Corpuscles,  Malpighian      .    .    .  206 

tactile     ....   26,  395 

Cough 303 

Cranial  nerves 35 

Cravate  de  Suisse 235 

Cricoid  cartilage 349 

Crico-thyroid,  etc.  (muscles)  .     .  350 


Cruor  of  the  blood     .    .    .      112, 113 

Crystalline  lens 426 

Curare  (action  of) 82 

Cylinder,  axis,  of  nerves    ...  26 

Cyon,  nerve  of 167 

D. 

Decussation  of  fibres  in  the  spinal 

cord 45 

Defecation 253,  279 

Depressor  nerves  of  the  heart      .  166 

Dermatoses 192 

Dermis 364 

Desquamation,  cutaneous  .     .     .  368 

intestinal    ...  260 

Diabetes 268 

Diagram  of  the  circulation      .  131,  143 
of  Hamberger     .  293 
of  the  muscle  .    .  68 
of  the  vessels  (vas- 
cular cones) 141 

Diaphragm 293,  339 

Diastase,  animal 217 

Diffusion 254 

gaseous 327 

Digestion 208 

Dilatation,  active,  of  vessels   .     .  173 

Ductus  arteriosus 517 

venosus 515 

Duct  of  Muller 459 

Duodenum 253 

Dyspepsia 243 

Dj'^speptoue 246 


E. 

Ejaculation 485 

Elasticity  of  muscles      .     .     .     74,81 

Elastic  tissue 98 

Electro-motor  (force)      ...      28,  73 

Electrotonus 31 

Enamel  (dental) 231 

Eiicephalon 55 

Endosmosis 259 

Endothelium 101,202 

Envelopes  (of  the  embryo)      .     .    4jy 

E|)ididymis 489 

Epithelium,  pulmonary  ....     283 

Epitheliums,  in  general       ...     184 

Equivalent,  mechanical,  of  heat .       78 

Erection  of  the  nipple    ....    364 

erectile  tissue   .     .      482,  483 

Evaporation,  cu'a'^'^.ous      .     .     .     342 

pulmonary    .       317,  343 

Excitability,  and  excitants     .     .      13 

of  the  muscle  ...      81 

of  the  spinal  cord    .      44 


INDEX. 


527 


Excitants  of  the  nervous  system  30 

Excitation,  latent 84 

Expiration,  force  of,  normal  .     .  305 

forcible 306 

or  exhalation   .     .     .  296 

Expiratory  nmscles 299 

Extract  of  beef,  Liebig's     .     .     .  213 


F. 


Facial  nerve 38 

Fallopian  tubes 492 

Fat  of  the  blood 128 

of  the  globules 12 

Fats,  absorption  of     .     .     .      255,274 

as  aliments 211 

Feathers 369 

Feces 276 

Fecundation 494 

Fibres,  nerve 25 

smooth  muscular    .    .     65,  92 

striated 67,  68 

Fibrine 125,  129 

Follicles,  closed 206 

pilous 369 

Food  substitutes 212 

Forces  (vital  forces,  forces  of  ten- 
sion)       322 

Forms,  natural,  of  arteries      .     .     152 

of  muscles      .    70,  72 

Fossae,  nasal 409 


G. 

Ganglia,  cardiac 169 

lymphatic   .    .    .      199,  205 

spinal 42 

semilunar 64 

Gases  of  the  blood 129 

Gasterase 239 

Generative  organs 477 

Glands,  in  general    .     .    .       191, 231 

lymphatic 206 

peptic 238 

svnovial  ....      104,  186 

Globules,'blood     ...     18, 113,  114 

different  kinds  of    .     .      18 

epithelial 18 

in  general 3-16 

lymph 196 

nerve 20,  24 

plasmatic    or  embry- 
onic    21,  96 

their  birth 9 

death     ....      12 

Globuline 117 

Globulines 197 

Glomeruli  of  Malpighius    .     .    .    150 


Glomerulus,  sudoriferous    .    .    .  373 

Glosso-v)haryngeal  (nerve)      .    .  405 

Glottidis,  rima 353 

Glottis 348 

Gluten 210 

Glycochol 282 

Glj^cogen  (substance)    ....  268 

Glycogeny 265,  268 

Glycoha3mia 271 

Grand  sympathy -tic 63 


H. 

Hallucinations 57 

Haptogenous  membrane     .     .     .  197 

Harmonics  (tones  of)      .    .      359,  422 

Hearing,  sense  of .     •    .     .     .     .  412 

Heart,  impulse  of 138 

Hematine  (hematosine)       .    .    .  118 

Hematoidine 118 

Hemine 118 

Hemispheres,  cerebral    ....  62 

Hemodromometer 147 

Hemodynamometer  .    ,    .    .     .  144 

Hemoglobuline 118 

Hemotachometer 147 

Humor,  aqueous 424 

vitreous 424 

Hunger 386 

Hydremia 122 

Hyperinosis 127 

Hypermetropia 431 

Hypincsis     .     .     .     .     ....     .  130 

Hypoglossal  nerve 40 


I. 


Ideas 57, 63 

Heum 248 

Hlusions,  optical 449 

Image  of  Purkinje 433 

Impermeability    (of  the    vesical 

epithelium) 193 

Impulse  of  the  heart 138 

Incus  (ear) 418 

Insalivation 216 

Inspiration,  force  of 290 

forcible 303 

Integument,  external    ....  364 

Integumentary  (envelopes)     .    .  186 

Intellect 63 

Intensity  (of  sounds)      .    .      358,  422 

Intercostal  (muscles)      .    .    .     .  2  '3 

Interference  (nervous)    ....  172 

Intermediate  nerve  of  Wrisberg  .  40  5 

Intestine,  large 275 

'  smaU 248 


528 


INDEX. 


Inuline 269 

Iris 438 

Irritability,  and  irritants    ...  14 

ofHaller     ....  81 

Iron  in  the  blood 118 


J. 


Jejunum 396 

Juice,  enteric 248 

gastric 238 

pancreatic 249 


K. 


Kyestelne 


471 


Lachrymal  system 454 

Laryngeal,  (nerve)  inferior     .    .  336 

superior  .    .  336 

Larynx 347 

Laws  of  Poiseuille 147 

Leucaemia 114 

Leucocytes 113 

Leucocytosis 114 

Lever  (for  mastication)      .     .    .  215 

in  the  skeletons    ....  101 

Lieberkiihn  glands  of    ...     .  232 

Ligaments  of  the  articulations     .  105 

Line,  primitive '    .  509 

Lingual  nerve 407 

Lips,  vocal . 355 

Liquor  sanguinis  ....      112,  125 

Littre,  glands  of 485 

Liver 232,  265 

Lobes,  pulmonary  lobules  .    .    .  283 

Locality,  sense  of 398 

Loss  of  blood 121 

Lymph 196 

Lymphatic  cone    .    .  * .    .    .    .  195 

sheaths 200 

spaces 202 

Lymphatics 194 


M. 

Macula  lutea 445 

Malleus  ear 417 

Mass  of  the  blood Ill 

Masseters  (muscles) 215 

Mastication 49,  214 

Mastoid  cells 419 

Matters,  extractive,  blood  .    .    .  128 

urine  .    .    .  470 


Maxillary  nerve,  inferior    ...  37 

superior      .    .  37 

Meatus  (nasal  fossae) 287 

IMechanism  of  muscles  ....  94 

Meconium 276 

Medulla  oblongata 48 

Membrana  vera,  etc 498 

Menstruation 334, 494 

Metals  in  the  blood 129 

Metapeptone 246 

Microzymes 130 

Micturition 475 

Milk 379 

Mimicry 362 

Mitral  valves 134 

Motor  oculi  com.  (nerve)    ...  36 

externus      ....  36 

Moulting,  epithelial 258 

Mountain  sickness 329 

Mucus,  in  general 194 

Murmur,  vesicular 312 

Muscae  volitantes 449 

Muscle,  ciliar}-- 436 

in  general 67 

Muscular  contraction     ....  85 

sense      ....     389,400 

Musculi  papillares  (heart)  ...  135 

Myography 85 

Myopia 431 


Nails 369 

Nausea  (sensations  of )  .     .    .    .    404 
Nerves,  centripetal  and  centrifu- 
gal...    .     29,40 

cranial 35 

Neurilemma 25 

Neuroglia 44 

Nipple 364,  379 

Nodule  of  Arantius 138 


Objective  cone 427 

Ocular  cone 427 

Odors 408 

Olfaction  or  smell 408 

Olfactory  (nerve) 35,  411 

Ophthalmic  nerve 37 

Optic  nerve 35,  37 

thalami 61 

Organs  of  the  senses 385 

Oscillations,  negative     ...     28, 80 

Ossicles  of  the  ear 418 

Otoliths 413 

Osmosis 259 

Ovale,  foramen 516 


INDEX. 


529 


Ovary 488 

Ovisac 490 

Oxidation  (in  the  organism)  .  .  322 
Oxide,  carbonic  (action  of )  120,  324 
Oxycarbonized  blood  ....  120 
Oxygen 129 


P. 


Pain 387 

Pancreas 249 

Pancreatine,  Pancrentogeny   .    .  250 

Panniculus  adiposus 97 

Papilla  of  the  optic  nerve    .    .    .  440 

Papillse,  lingual 403 

nerve 405 

Paralysis,  vaso-motor    ....  172 

Parapeptone 246 

Patches,  Peyers 206 

Patheticus  (nervus) 36 

Pepsin 239 

Peptogeny 242 

Peptones 245 

Perceptions 59 

Peristaltic  movements    ....  253 

Peristal  tism  of  the  vessels  .     .     .  175 

Pharynx 224 

Phenomena,  chemical,     of     the 

muscle  ...     72, 77 
chemical,  of  the  nerve   27 

Phonation 347 

Physiology,  definition  of    .    .    .  1 

Pitch  of  notes 422 

Placenta 506 

Plasmine 130 

Plates,  motorial 26 

Pleasure 383 

Plexus,  solar 277 

Pneumic  acid 328 

Pneumo-gastric 39,  336 

Pneumonia,  office  of  the  epithe- 
liums in 192 

Poiseuille,  laws  of 147 

Presbyopia  or  presbytia      .    .     .  431 

Pressure,  atmospheric    ....  106 

in  respiration  ....  309 

of  the  blood     ....  142 

sensations  of  ...    .  397 

Processes,  ciliarj' 438 

Prostate  and  prostatic  gland   .    .  475 

Protagons 27 

Ptyal'ine 217 

Pulmonary  capacity 306 

cone 287 

mucous  surface     .    .  281 

Pulse 155 

Punctum  coRCum 144 

Pupil  of  the  eye 439 

Pyramids 45 


R. 

Radiation  of  light 449 

Recurrent  sensibility 41 

Reduction,  phenomena  of  .    .    .  322 

Reflex  phenomena,  in  general     .  28 

centres  of      .  46 

classification  of  51 

Refraction  (eye) 426 

Registers  (vocal) 358 

Relation,  functions  of     ....  347 

Resonance,  arrangements  for  .    .  357 

Respiration 281 

Rtte  Malpighianum 186 

mirabile .  150 

Retina 440 

Ribs 289 

Rigidity,  cadaveric   ....     71,  82 

Elma  qlottidis 353 

Rodents 215 

Roots  of  nerves 40 

Ruminants 215 


s. 


Sncculus 421 

Saliva 216 

Sarcous  elements 68 

Satiety 387 

Savors 410 

Sclerotic  coat 435 

Scurf,  epidermal 368 

Sebaceous  glands 378 

Sebum 379 

Segmentation  o{  glohvies   ...  10 

ovum  ....  10 

Semicircular  canals 413 

Seminiferous  tubes 478 

Sense,  muscular 389 

Sensations,  associated  ....  57 
general  ....  56,  386 
localized  ....  56,  391 

special 391 

subjective    ....  55 

Sensibility,  general  .....  55 

recurrent     ....  41 

Serine 130 

Serous  membranes    ....  185, 193 

Serum 127,128 

Sheaths,  lymphatic 200 

Sickness,  mountain 329 

Skin 364 

Sinus,  uro-genital 458 

venous 163 

Smell 408 

Sneezing 47,  303 

Solar  plexus 277 

Soprano  (voice) 359 

Soufile,  vascular 165 


34 


530 


INDEX. 


Sounds  (glottid) 356 

in  the  vessels    ....     16-4 

of  the  heart  .    .    .      138,  141 

respiratory  and  vesicular    3 12 

Spaces,  perivascular  ....  195,  202 

Spectroscopy  (of  the  blood)     .    .    119 

Speech 49 

Spermatic  fluid      ....      480,  487 

Spermatozoids 479 

Sphincter  of  the  urethra      .    .    .     474 
Sphincters  of  the  anus    ....    278 

Sphj'gniograph 157 

Spinal  accessory  nerve  of  Willis  .    362 

cord 31,  42 

nerves 40 

Spirometer 306 

Spleen 206 

Spot,  vellow 442 

Stapes  (ear) 418 

Stomach 233 

Straining,  or  effort    .    .    .      280,  302 

Struggle  (vocal) 362 

Sudoric  acid 375 

Sudoriferous,     or     sudoriparous, 

glands 373 

Sugar  of  milk 381 

Sulphocyanide  of  potass,  in  saliva  218 

Sweat 374 

Synchronism  of  movements  of  the 

heart 141 

Synovial  fluid,  etc.    .     .    .      104,  188 

System,  auricular 133 

nervous 24 

ventricular 134 


Tactile  corpuscles 394 

Taste 386 

Taurine 262 

Tears 456 

Temperature,  of  the  blood  .    .    .  320 

body    .    .    .  3;J9 

sensations  of .    .     .  396 

Temporal  muscle 215 

Tendons 98 

Tenesmus 387 

Tenor  (voice) 359 

Tension,  forces  of 314 

Testicle 478 

Tetanus 76 

physiological    ....  86 

Thalami  oplici 61 

Thelne 213 

Thoracic  cage 289 

Tissue,  cellular  and  connective    .  94 

respiration  of     ....  322 


Tone,  of  notes,  of  the  voice     .    .    359 

Tongue    . 401 

Tonicity,  muscular    ....     70,  73 

Tonsils 230,  379 

Tonus  of  vessels 172 

Touch,  sense  of 384 

Trachea 282,301 

Transfusion  of  blood 121 

Tricuspid  valves 134 

Tube,  Eustachian 419 

Fallopian 492 

Turbinated  bones  (nares)   .    .    .    409 
Tympanum 416 


u. 

Urachus 459 

Urea 128,  198 

Urethra 475 

Uric  acid 128,  470 

Utricle  (internal  ear)      ....    412 
prostatic       478 


V. 

Vagina 494 

Valve,  ileo-coecal 275 

in  veins 164 

Variations  in  the  mass  of  the  blood  112 
Variation,  negative  .    .     .     .     28, 82 

Vascular  cone 141,  152 

Vaso-motors 66, 170 

Vems  (fluid) 164 

(portal) 150 

(vessels) 16-J 

Velocity  of  the  circulation  .    .    .    146 

Venous  plexus 163 

Ventilation  of  lungs 311 

Ventricle  of  heart 1-54 

Vernix  caseosa 38i 

Vesicles,  cerebral  (foetus)    ...    509 

Graafian 490 

pulmonary 283 

umbilical 500 

Vibratile  cells  (cilia)      ....    187 

Vibrations,  nerve 30 

sonorous      ....    422 

Villi 191,254 

Vital  spot 49,  336 

Vitellus 491 

Vocal  cords 348,  355 

Voice  (head  and  chest  tones)  .    .    356 

Volition 57,  03 

Vomiting 236 

Vowels y60 


INDEX. 


531 


Walking 49,  107 

"Wave  pulsation 155 

Will 57,63 

Wolffian  body 459 


Womb 492 

Woorara,  action  of 82 


Zoamyline 


Cambridge:  Press  of  John  Wilson  &  Son. 


A    CATALOGUE 

OF 

MEDICAL    WORKS 

PUBLISHED   BY 

JAMES    CAMPBELL, 

Publisfjet  anti  iSookscIler, 

1 8  Tremont  Street,  Museum   Building  {directly  opposite 
Messrs.  Codman  Or*  Shurtleff's),  Boston,  Mass. 


A  CONTRIBUTION  TO  THE  TREATMENT  OF 
THE  Versions  and  Flexions  of  the  Unimpregnated  Uterus.  By 
Ephraim  Cutter,  M.D.  Twenty-four  Illustrations.  Second  edition, 
entirely  rewritten.     i6mo,  cloth.     ^1.50. 

"  This  is  an  excellent  pamphlet  on  a  difficult  subject,  enriched  with  many  dia- 
grams of  the  uterine  organs,  and  the  pessaries  recommended  by  the  author.  We  do 
not  remember  to  have  seen  a  clearer  exposition  of  the  subject  in  any  work,  and  can 
heartily  recommend  this  for  perusal."  —  The  Medical  Press  and  Circular,  Edin- 
burgh, Jan.  31,  1872. 

THEORY    OF    MEDICAL   SCIENCE :    The  Doctrine 

of  an  Inherent  Power  in  Medicine  a  Fallacy.    By  William  R.  Dunham, 

M.D.     i6mo,  cloth.     $1.25. 

Dr.  Edward  H.  Clarke,  formerly  Professor  of  Materia  Medica  in  Harvard  Uni- 
versity, writes  the  author:  "I  have  read  your  book  with  much  satisfaction.  It  is 
always  pleasant  to  see  one  combat  an  error  with  energy  and  skill.  You  make  your 
[loints  with  great  distinctness,  and  support  them  with  great  ability.  It  was  always 
my  endeavor,  in  my  lectures  on  Materia  Medica,  to  insist  as  strongly  as  I  could  that 
drugs  possessed  in  themselves  no  occult  power,  but  that  what  is  called  their  physio- 
logical action  is  the  result  of  the  reaction  of  the  system  upon  the  drug,  as  the  latter 
passed  through  the  former." 

C.  E.  HOBBS'S  BOTANICAL  HAND-BOOK  of  Com- 

mon  Local  English  Botanical  and  Pharmacopoeial  Names,  arranged  in 
Alphabetical  Order,  of  most  of  the  Crude  Vegetable  Drugs,  &c.,  in  common 
Use :  their  Properties,  Productions,  and  Uses,  in  an  Abbreviated  Form. 
8vo,  cloth.     ^3.50. 

"  Every  druggist  and  druggist's  assistant  should  have  a  copy." 


2  Catalogue  of  Medical   Works. 

FILTH    DISEASES    AND   THEIR    PREVENTION. 

By  John  Simon,  M.D,,  F.R.C.S.,  Chief  Medical  Officer  of  the  Privy 
Council  and  the  Local  Government  Board  of  Great  Britain.  First  Amer- 
ican edition.  Printed  under  the  direction  of  the  State  Board  of  Health  of 
Massachusetts.     i6mo,  cloth,     ^i.oo. 

**  The  undersigned  members  of  the  Massachusetts  State  Board  of  Health  would 
respectfully,  but  earnestly,  urge  upon  all  persons  the  careful  perusal  of  the  following 
masterly  essay  by  Mr.  Simon,  Chief  Medical  Officer  of  the  Privy  Council  and  of  the 
Local  Government  Board  of  England.  If  the  practical  suggestions  made  therein 
were  acted  on  by  all  citizens,  hundreds  of  lives  now  annually  doomed  to  destruction 
would  be  saved,  and  the  health  and  comfort  of  the  people  greatly  increased." 

Henry  I.  Bowditch,  R.  T.  Davis, 

Richard  Frothingham,  Daniel  L.  Webster, 

J.    C.    HOADLEY,  J.    B.    NeWHALL, 

W.  L.  Richardson,  Sec'y  pro  tem. 
Members  of  the  State  Board  of  Health  of  Massachusetts. 

A   COURSE    OF    LECTURES    ON    PHYSIOLOGY, 

delivered  at  the  University  of  Strasbourg.  By  E.  KUss,  Professor  of  the 
Faculty  of  Medicine.  Edited  by  Dr.  Mathias  Duval,  Prosector  to  the 
Faculty  of  Medicine  at  Strasbourg.  Translated  from  the  revised  edition 
by  Robert  Amory,  Lecturer  on  Physiology  at  the  Maine  Medical  School. 
I  vol.,  i2mo,  cloth.     Illustrated  with  152  wood-cuts.     Price  ^2,50. 

"  We  consider  the  book  to  be  the  best  of  all  the  later  text-books  of  human  phys- 
iology that  can  be  placed  in  the  hands  of  the  American  student,  and  we  cordially 
urge  its  adoption  as  a  manual  by  those  engaged  in  teaching  this  intricate  and  deeply 
interesting  branch  of  science.  Though  concisely  written,  many  of  its  topics  are  quite 
elaborately  treated."  —  A  merican  Journal  of  Medical  Sciences. 

"  When  we  say  that,  in  our  opinion,  it  is  the  best  book  that  a  student  can  procure, 
we  only  state  that  which  is  not  only  our  firm  conviction,  but  that  of  other  teachers 
also."  —  Medical  Press  and  Circular. 

"  M.  Kiiss  was  one  of  those  modest  scientists  who  love  science  for  itself ;  who 
seek  for  the  truth  without  caring  whether  they  are  well  spoken  of  by  the  world."  — 
Gazette  Hebdomadaire. 

"  Professor  Kuss's  work  seems  to  us  to  be  the  best  students'  manual  that  we  have 
yet  seen."  —  Medico-Chirurgical  Review. 

"  After  a  careful  reading  of  the  book,  we  do  not  hesitate  to  call  it,  on  the  whole, 
the  best  treatise  on  Physiology,  of  its  size,  now  to  be  found  in  English.  Kuss's  style 
is  full  of  vivacity  and  elegance,  and  abounds  in  picturesque  epithets  and  bits  of  descrip- 
tion, which  serve  both  to  fix  the  reader's  attention  and  to  impress  his  memory."  — 
Boston  Medical  and  Surgical  fourttal. 


Catalogue  of  Medical   Works,  3 

ANATOMY    OF    THE    INVERTEBRATA.      By    C. 

Th.  V.  SiEBOLD.  Translated  from  the  German,  with  Additions  and  Notes, 
by  Waldo  T.  Burnett,  M,D.  i  vol.,  8vo,  cloth,  bevelled  boards,  gilt 
top.    $5.00. 

"The  translation  is  effected  in  a  very  satisfactory  manner ;  the  language  is  clear, 
and  conveys  the  full  meaning  of  the  author,  without  retaining  the  German  idiom. 
The  editor  has  enriched  it  with  numerous  references,  and  original  notes  greatly 
increase  the  value  of  the  work.  We  have  not  the  least  doubt  that  the  work  will 
speedily  supersede  every  text-book  of  Comparative  Anatomy  which  has  yet  appeared." 
—  Association  Medical  yournal,  Lottdon- 

This  is  beheved  to  be,  with  the  editor's  valuable  and  extensive  notes,  incomparably 
the  best  and  most  complete  work  on  the  subject  extant,  and  as  such  it  is  commended 
by  Profs.  Agassiz,  Silliman,  Hitchcock,  and  other  scientific  and  medical  men. 

Agassizsays:  "There  is  no  other  work  in  any  language  that  will  bear  any  com- 
parison with  this,  in  the  fulness  and  accuracy  of  its  descriptions  of  organs,  in  the 
amount  and  value  of  the  microscopic  investigations  whose  results  it  embodies,  or  in 
the  masterly  and  comprehensive  manner  in  which  all  its  results  are  systematized, 
and  their  subjects  classified  and  grouped." 

THE  PROBLEM  OF  HEALTH  AND  HOW  TO 

Solve  It.     By  Ruben  Greene,  M.D.     i2mo,  cloth.    $1.50. 

'"The  Problem  of  Health'  is  a  medical  work,  treating  of  sanitary  science,  stimu- 
lants, narcotics,  sleep,  exercise,  dress,  the  value  of  sunlight,  and  many  other  health 
topics,  concerning  which  a  large  amount  of  information  is  imparted."  —  Cape  A  nn 
Advertiser.^  Gloucester.,  Mass. 

TRANSACTIONS   OF  THE  AMERICAN  OTOLOG- 

ICAL  Society.     Published  annually.    8vo,  pamphlet.     $1.25. 


THE    DUBLIN    PRACTICE   OF    MIDWIFERY.     By 

Henry  Maunsell,  M.D.,  formerly  Professor  of  Midwifery  in  the  Royal 
College  of  Surgeons  in  Ireland.  New  edition.  Numerous  Illustrations. 
i2mo,  cloth.     $1.75. 

THE   HAND-BOOK   FOR   MIDWIVES.     By  Henry 

Fly  Smith,  B.A.,  M.B.,  Oxon.,  M.R.C.S.,  Eng.,  late  Surgeon-accoucheur 
to  the  St.  James  Dispensary,  late  Assistant-Surgeon  at  the  Hospital  for 
Women,  Soho  Square.     41  Illustrations.      i6mo,  cloth.     ?/.75. 


4  Catalogue  of  Medical   Works. 

THE    PASSIONS     IN     THEIR    RELATIONS    TO 

Health  and  Disease  :  Love  and  Libertinism.  Translated  from  the 
French  of  Dr.  X.  Bourgeois,  Laureate  of  the  Academy  of  Medicine  of 
Paris,  &c.  By  Howard  F.  Damon,  A.M.,  M.D.  i6mo,  cloth,  pp.  224. 
J551.25. 

The  following  are  a  few  of  the  notices  which  have  been  received:  — 
"  There  is  a  world  of  suggestions  for  the  management  of  the  passions  in  this  book, 
and  their  perusal  will  not  fail  to  work  personal  profit."  —  Massachusetts  Ploughman. 
'■  There  is  a  delicacy,  frankness,  candor,  and  evident  sincerity  about  the  composi- 
tion, that  convince  even  the  casual  reader  that  the  author  and  translator  have  only 
the  welfare  of  their  fellow-men  at  heart.  It  is  a  treatise  on  Love  and  Libertinism, 
in  a  right,  proper,  and  intelligent  spirit,  and  of  incalculable  benefit  to  the  whole  com- 
munity." —  The  Commonwealth. 

"  The  book  bears  no  trace  of  the  morbid,  unhealthy  spirit  characteristic  of  many 
French  books  upon  this  subject."  — Boston  fournal. 

COMPARATIVE    ANATOMY   AND    PHYSIOLOGY 

of  the  Vertebrate  Animals.     By  Richard  Owen,  F.R.S.,  Superin- 
tendent of  the  Natural  History  Departments,   British  Museum.     3  vols., 
8vo,  with  1,472  wood-cuts.     ^25.00. 
Vol.      1.  —  Fishes  and  Reptiles^  with  452  wood-cuts. 
Vol.    II.  —  Warm-Blooded  Vertebrates,  with  466  wood- cuts. 
Vol.  III.  — Mammalia,  including  Man,  with  copious  indexes  to  the  whole 
work,  and  614  wood-cuts. 

PHOTOGRAPHS    OF    THE    DISEASES    OF    THE 

Skin.  Taken  from  Life,  under  the  Superintendence  of  Howard  F.  Da- 
mon, M.D.  I'hotographs,  complete  (24  Photographs,  with  letterpress  de- 
scription), quarto,  half  morocco,  $12.00 ;  each  photograph,  without  letter- 
press, 50  cents. 

SURGICAL    CLINIC    OF    LA   CHARITE.     Lessons 

upon  the  Diagnosis  and  Treatment  of  Surgical  Diseases.  Delivered  in  the 
month  of  August,  1865,  by  Prof.  Velpeau.  Collected  and  edited  by  A. 
Regnard,  Interne  des  H6pitaux.  Revised,  by  the  Professor.  Translated 
by  W.  C.  B.  FiFiELD,  M.D.     One  volume,  i6mo,  cloth.     $1.00. 

HAND-BOOK  OF  THE   DISEASES  OF  THE  EYE. 

Their  Pathology  and  Treatment.  By  A.  Salomons,  M.D.,  Fellow  of  the 
Massachusetts  Medical  Society,  former  Oculist  in  Government  Service  at 
Veenhuizen,  Holland,  &c.  One  volume,  i6mo.  Colored  plate.  English 
cloth.     $1.50. 


Catalogue  of  Medical   Works.  5 

METHOMANIA:    A   Treatise  on  Alcoholic   Poisoning. 

By  Albert  Day,  M.D.,  Superintendent  of  the  New  York  State  Inebriate 
Asylum.  One  volume,  i6mo.  Pamphlet,  40  cents;  cloth,  bevelled  boards, 
60  cents. 

VERATRUM   VIRIDE    AND   VERATRIA :    A    Con- 

tribution  to  the  Physiological  Study  of.  With  experiments  on  Lower  Ani- 
mals, made  at  La  Grange  Street  Laboratory,  1869.  By  Robert  Amory, 
M.D.,  and  S.  G.   Webber,   M.D.    One  volume,  i6mo.    Pamphlet,  50 

cents ;  cloth,  75. 

NITROUS    OXIDE :  Physiological  Action  of,  as  shown 

by  Experiments  on  Man  and  the  Lower  Animals.  By  Robert  Amory, 
M.D.,  of  Longwood,  Mass.  Illustrated  by  Pulse  Tracings  with  the  Sphyg- 
mograph.     PampUet,  8vo,  pp.  31.     50  cents. 

TWO    CASES    OF    GESOPHAGOTOMY   FOR    THE 

Removal  of  Foreign  Bodies.  With  a  History  of  the  Operation. 
Second  edition  with  an  additional  Case.  By  David  W.  Cheever,  M.D., 
Adjunct  Professor  of  Clinical  Surgery  at  Harvard  University,  Surgeon  to 
the  Boston  City  Hospital.     One  volume,  8vo,  cloth.     75  cents. 

CONTRIBUTIONS    TO    DERMATOLOGY.     Eczema, 

Impetigo,  Scabies,  Ecthyma,  Rupia,  Lupus.  By  Silas  Durkee,  M.D., 
Consulting  Physician,  Boston  City  Hospital.     Pamphlet,  8vo.     ^1.50. 

PHYSIOLOGICAL  AND  THERAPEUTICAL  Ac- 
tion and  Value  of  the  Bromide  of  Potassium  and  the  Bromide 
OF  Ammonium.     Illustrated  by  Experiments  on  Man  and  Animals. 

In   Two  Parts. 

Part  I. — The  Physiological  and  Therapeutical  Action  and  Value  of  the 
Bromide  of  Potassium  and  its  kindred  salts.  By  Edward  H.  Clarke, 
M.D.,  Professor  of  Materia  Medica  in  Harvard  University. 

Part  II. — Experiments  illustrating  the  Physiological  Action  of  the  Bro- 
mide of  Potassium  and  Ammonium  on  Man  and  Animals.  By  Robert 
Amory,  M.D.,  Annual  Lecturer  for  1 870-1 871  on  the  Physiological  Action  of 
Drugs  in  the  Medical  Department  of  Harvard  University.  One  volume,  i6mo, 
cloth.     Si.so. 


6  Catalogue  of  Medical   Works, 

NEW    TREATMENT    OF    VENEREAL    DISEASES 

AND  OF  Ulcerative  Syphilitic  Affections  by  Iodoform.  Trans- 
lated from  the  French  of  Dr.  A.  A.  Izard.  By  Howard  F.  Damon, 
M.D.     Pamphlet,  i6mo.     50  cents. 

THE    GYNECOLOGICAL    RECORD.      A   Book   of 

Blank  Forms,  intended  as  an  aid  to  the  busy  practitioner,  in  recording  gynze- 
cological  cases,  with  an  Introduction  and  Appendix  of  blank  leaves,  and 
tables  for  the  ready  analysis  of  the  contents  of  the  book.  Prepared  by 
Joseph  G.  Pinkham,  A.M.,  M.D.,  Corresponding  Member  of  the  Gynae- 
cological Society,  Fellow  of  the  Massachusetts  Medical  Society.  Approved 
by  the  Gynaecological  Society.  One  volume,  quarto,  half-bound.  ^2.50. 
Postage,  50  cents  extra.     The  Blanks,  per  quire,  50  cents. 

PHYSICIAN'S     REGISTER,     FOR     OFFICE     OR 

Hospital  Practice.  An  Imperial  8vo  book  of  Blank  Forms,  similar  to 
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age,  and  disease,  with  a  large  blank  space  for  remarks.  Price  ^1.50.  25 
cents  extra  when  sent  by  mail. 

HISTORY   OF   MODERN  ANESTHETICS.     By  Sir 

James  Y.  Simpson,  of  Edinburgh.  A  reply  to  Dr.  Jacob  Bigelow's 
second  letter.  Reprinted  from  the  Journal  of  the  Gynaecological  Society  of 
Boston,  May,  1870.     Pamphlet,  8vo.    25  cents. 

THE  PHYSIOLOGY  OF  WOMAN  AND  HER  Dis- 
eases FROM  Infancy  to  Old  Age.  Including  all  those  of  her  critical 
periods,  —  Pregnancy  and  Childbirth,  —  their  causes,  symptoms,  and  appro- 
priate treatment ;  with  hygienic  rules  for  their  Prevention,  and  the  Preser- 
vation of  Female  Health.  Also,  the  management  of  Pregnant  and  Parturient 
Women,  by  which  their  pains  and  perils  may  be  greatly  obviated.  To  which 
is  added  a  Treatise  on  Womanhood  and  Manhood,  Love,  Marriage,  and 
Hereditary  Descent ;  being  the  most  approved  views  of  modern  Times. 
Adapted  to  the  instruction  of  females.  In  three  books.  Complete  in  one 
volume.  By  C.  Morrill,  M.D.,  author  of  supdry  Medical  Essays,  Lect- 
ures on  Popular  Physiology,  &c.  Eleventh  edition.  One  volume,  i2mo, 
cloth.    ^1.50. 

THE    HISTORY   AND    PHILOSOPHY   OF    MAR- 

riage;  or.  Polygamy  and  Monogamy  Compared.  By  a  Christian 
Philanthropist.     New  and  revised  Edition.     One  volume,  i6mo,  256  pp. 


Catalogue  of  Medical   Works.  7 

JOURNAL  OF  THE  GYNECOLOGICAL  SOCIETY 

OF  Boston.  A  Monthly  Journal,  devoted  to  the  Advancement  of  the 
Knowledge  of  the  Diseases  of  Women.  Edited  by  Winslow^  Lewis, 
M.D.,  H.  R.  Storer,  M.D.,  Geo.  H.  Bixby,  M.D. 

First  number  was  published  July^  1869.     A  few  volumes  still  remain 

for  sale  at  the  prices  given  below:  — 

Vol.        I,  —  From  July  to  December,  1869,  cloth  .         .        .         .  ^2.50 

Vol.     II.  —  From  January  to  July,  1870,  cloth      ....  2.50 

Vol.    in.  —  From  July  to  December,  1870 2.50 

Vol.    IV.  —  From  January  to  July,  1871 2.50 

Vol.      V.  —  From  July  to  December,  1871 2.50 

Vol.    VI.  —  From  January  to  July,  1872 2.50 

Vol.  VII.  —  From  July  to  December,  1872 2.50 

DISEASES  OF  THE  WOMB.  Uterine  Catarrh  fre- 
quently the  Cause  of  Sterility.  New  Treatment  By  H.  E.  Gantillon, 
M.D.     Pamphlet,  8vo.     50  cents, 

"  This  little  brochure  is  well  worthy  the  study  of  all  who  are  interested  in  Gynae- 
cology." —  .S"^.  Louis  Medical  and  Surgical  Journal. 

THE    DETECTION     OF    CRIMINAL    ABORTION, 

AND  THE  Study  of  Fceticidal  Drugs.  By  Ely  Van  de  Warker, 
M  D.  Illustrated  by  Pulse  Tracings  with  the  Sphygmograph,  Pamphlet, 
8vo.     50  cents. 

"  It  is  a  very  sensible  and  thorough  treatise  on  this  important  subject,  and  should 
be  read  by  the  profession  everywhere  "  —  Boston  Journal  0/  Chemistry. 

THYROTOMY  FOR  THE  REMOVAL  OF  LARYN- 
GEAL Growths.  Modified.  By  Ephraim  Cutter,  M.D.  Illustrated. 
Pamphlet,  8vo.     50  cents. 

FEMALE    HYGIENE.     A   Lecture  delivered  at   Sacra- 
mento and  San  Francisco.    By  Horatio  R.  Storer,  M.D,    Pamphlet, 
8vo,     25  cents. 
"  It  IS  not  only  an  admirable  treatise  on  a  subject  on  which  the  author  is  especially 

qualified  to  write,  but  it  also  does  good  service  in  combating  the  woman  suffrage 

delusion."  —Boston  Traveller ^  March,  18,  1872. 


The  Publisher  would  invite  the  attention  of  the  public  to 
the  following  admirable  reviews  of  Dr.  Simon's  book 
ON  Filth  Diseases,  and  would  urge  upon  every  07ie 
the  importance  of  a  careful  examination  of  the  book 
itself 

From  the  Boston  Traveller. 

It  is  comparatively  rare  that  a  work  by  a  thoroughly  scientific  medical  man  comes 
from  the  press  in  such  a  shape  as  to  be  of  practical  value  to  the  non-professional  reader. 
Either  from  the  terminology  employed,  or  the  subject  treated,  medical  books  and 
reports  are  only  to  be  found  on  the  shelves  of  the  physician's  library.  Such  is  not, 
or  should  not,  be  the  case  with  a  small  volume  recently  published  by  James  Campbell, 
of  this  city,  it  being  the  American  reprint  of  a  most  masterly  essay  by  John  Simon, 
chief  medical  officer  of  the  Privy  Council  and  of  the  Local  Government  Board  of 
England.  The  essay  is  most  cordially  commended  by  the  members  of  the  State  Board 
of  Health  of  Massachusetts,  and  certainly  no  intelligent  householder  should  fail  to  read 
it  carefully,  and  profit  by  the  information  contained  in  its  pages.  Its  title,  "Filth 
Diseases  and  their  Prevention,"  indicates  the  particular  line  of  investigation  followed 
by  Dr.  Simon;  and  his  conclusions,  based  on  statistics  and  results  of  careful  investi- 
gation, are  thoroughly  logical.  He  assumes  at  starting  that  the  ralson  d'etre  of  sanitary 
authorities,  like  our  boards  of  health,  is  the  fact  that  very  much  disease  is  preventable; 
and  that  it  is  true  that  the  mortality  from  diseases  is  vastly  greater  than  it  would  be 
if  the  existing  knowledge  of  the  causes  of  disease  were  applied.  Of  all  tlie  removable 
causes  of  disease,  Dr.  Simon  justly  considers  the  chief  to  be  uncleanliness :  that  is, 
first,  the  non-removal  of  refuse  matters ;  and,  second,  the  license  permitted  to  cases 
of  infectious  disease  to  scatter  the  seeds  of  infection.  He  says  that  a  bad  odor  is  by 
no  means  a  sure  warning  against  the  presence  of  poisonous  matters.  That  they  may 
exist  without  any  odor  whatever,  and  that  disinfection  by  no  means  consists  in  covering 
up  one  bad  smell  by  another  equally  offensive  but  more  pronounced.  He  goes  thor- 
oughly into  the  subject  of  disinfection,  and  shows  just  how  it  should  be  done  to  be  of 
any  value.  Interesting  cases  are  quoted,  showing  in  what  subtle  ways  these  ferment 
poisons,  such  as  cause  typhoid  fever,  are  spread  abroad,  manifesting  their  results  miles 
and  miles  away  from  their  source,  being  carried  in  air,  water,  milk,  and  other  vehicles 
suitable  to  preserve  their  vitality.  The  subjects  of  typhoid  fever  and  cholera  are  quite 
fully  discussed  in  relation  to  their  preventability,  as  well  as  the  relation  of  cause  and 
effect  which  filth  may  bear  to  consumption. 

A  large  portion  of  the  essay  is  devoted  to  the  question  of  house  drainage  and  pub- 
lic sewerage,  with  suggestions  of  the  utmost  importance  to  every  householder.  Yir. 
Simon  shows  just  how  and  in  what  particular  way  the  public  sewers,  when  insufficient 
or  defectively  ventilated,  may  become  exceedingly  dangerous.  Apropos  of  this  subject 
of  ventilation  of  sewers,  it  is  interesting  to  see  how  his  judgment  coincides  with  tliat  of 
the  gentlemen  who  opened  the  rain  pipes  into  the  sewers,  in  1874,  in  this  city,  and  for 
which  they  have  been  soundly  abused  by  some  medical  men,  particularly  by  one  re- 
cently in  the  columns  of  a  morning  paper.  That  writer  made  out  a  frightful  increase 
in  mortality  by  comparing  statistics  of  1S74  and  1875,  when,  as  he  admits,  the  rain 
pipes  were  let  into  the  sewers  during  both  years.  He,  however,  unfortunately  for  his 
argument,  took  the  total  mortaUty  instead  of  the  mortality  from  zymotic  diseases. 
Now,  he  can  liardly  claim  that  sewer  gas  causes  apoplexy  or  heart  disease  ;  and,  if  he 
takes  only  the  diseases  which  can  be  claimed  to  be  caused  by  filth,  he  will  find  a  very 
gratifying  decrease  in  the  mortality  in  the  first  three  months  of  1S75  when  the  sewers 
were  ventilated,  as  compared  with  tlie  same  months  in  1874  when  they  were  not.  It 
is  sim])ly  because  the  sewers  are  not  yet  sufficiently  ventilated  that  we  occasionally 
notice  the  offensive  odors.  Dr.  Simon  considers  this  matter  of  ventilation  of  sewers 
of  the  utmost  importance.  His  essay  is  delightfully  clear,  and  free  from  technical 
terms,  and  can  be  read  with  pleasure  and  profit  by  every  person  of  ordinary  intelligence ; 
and,  if  landlords  will  dCt  on  his  suggestions,  much  sickness  and  death  may  be  prevented. 


SURGICAL    CLINIC    OF  LA    CHARItL 


LESSONS 


UPON   THE 

DIAGNOSIS    AND    TREATMENT 
OF  SURGICAL   DISEASES, 

Delivered  in  the  month  of  August^  1865,  by  Prof.  Veipeau. 

collected  and  edited  by  a.  regnard,  interne    des    hos 
pitaux.     revised  by  thf  professor. 

Translated   by  W.   C.   B.   FIFIELD,   M.D. 

I  volume.'     i6mo.     Cloth.     $i.oo. 


NOTICES    OF    THE     PRESS. 

*'This  modest  little  book  contains  a  statistical  rSsumS,  by  the  author,  of  his  sur- 
gical experience  in  tlie  hospital  wards  under  his  care  during  the  year.  He  treats  his 
subject  under  the  successive  headings:  Generalities,  Fractures,  Affections  of  the 
Joints,  Inflammation  and  Abscesses,  Affections  of  the  Lymphatic  System,  Bums  and 
Contusions,  Affections  of  the  Genito-Urinary  Organs,  Affections  of  the  Aural  Region, 
Affections  of  the  Eyes.  Statistics  of  Operations.  We  have  a  special  liking  for  such 
works,  which  give  us  the  most  authoritative  opinions  of  the  elders  of  the  medical  pro- 
fession, who  have  reached  the  time  when  the  judgment  is  least  biased  by  the  rivalries 
and  personal  influences  which  are  so  apt  to  mislead  younger  minds.  It  is  o  vastly 
more  value  than  many  more  ambitious  and  bulky  works."  —  Bostoti  Medical  and 
Surgical  Jourftal. 

"  He  not  unfrequently  surprises  us  by  the  simplicity  of  his  expedients  for  the  aid 
of  '  Nature  in  Disease,'  and  rarely,  if  ever,  fails  in  making  out  his  case.  As  a  whole, 
the  work  is  not  only  instructive,  but  entertaining,  and  may  be  regarded  as  one  of  oar 
landmarks  of  minor  surgery,  upon  our  skill  in  which  much  of  our  success  will  be 
found  to  depend."  —  Medical  Record. 

*'  It  is  rare  that  so  small  a  book  contains  so  many  suggestions  of  great  practical 
worth,  and  throws  so  much  light  on  certain  debated  points,  as  Velpeau's  Lessons. 
Though  nominally  a  review  of  one  year's  practice,  it  is  in  reality  an  epitome  of  the 
experience  of  a  lifetime."  —  Detroit  Review. 

"All  who  value  the  teachings  of  this  great  man  will  not  lose  the  opportunity  of 
obtaining  them,  as  presented  in  this  brief  and  economical  iorm.'^  —  R ichmond  Medr 
cal  Jourttal. 

Sent  by  mail^  postage  prepaid^  on  receipt  of  advertised  price, 

JAMES   CAMPBELL,  Publisher,     . 
18  Tremont  Street.,  Museum  Build  tug,  Boston,  Mass. 


NEW   BOOK    ON    THE    EYE. 


HAND    BOOK 

OF    THE 

DISEASES  OF  THE  EYR 

C})eir  ipatl)alagg  auO  Creatmeut* 

BY 

A.    SALOMONS,    M.D., 

Fellow  of  the  Massachusetts  Medical  Society ;  former  Oculist  in  Government  Service 
at  Veehnhizen,  Holland,  &c. 

One  volume,  i6mo.     Colored  f  late,     English  cloth.     $1.50. 


PREFACE. 
"  The  book  is  divided  into  two  parts :  the  first  includes  the 
pathology  and  treatment  of  eye  diseases;  and  the  second,  the 
operative  surgerj  of  the  eye.  The  practical  portions  of  the  work 
are  given  with  as  much  detail  as  possible,  and  from  the  expe- 
rience of  the  author;  and  it  is  hoped  they  may  prove  a  useful 
guide,  not  only  to  those  entering  this  interesting  department 
of  medicine,  but  also  to  the  basy  practitioner,  wlio  finds  himself 
unable  to  peruse  the  more  elaborate  treatises  on  this  subject." 

From  the  Philadelphia  Medical  and  Surgical  Reporter. 

**  A  synopsis  like  this,  which  goes  over  so  much  ground  in  so  small  a  space,  is 
advantageous  to  the  student,  in  connection  with  clinical  studies,  and  the  perusal  of 
more  extended  treatises.  The  definitions  are  carefully  given,  accuracy  is  observed, 
and  lucidity  is  not  sacrificed  to  brevity.  The  operations  reconnnended  are  carefully 
selected  and  described.     That  for  Entropium  we  may  particularly  mention  as  in  point." 


For  sale  by  all  medical  booksellers.,  or  sent  by  ruail^   -postage 
prepaid,  on  receipt  of  advertised  p>rice. 

JAMES   CAMPBELL,  Publisher, 

Boston^  Mass 


^^Ptof,  Kuss's  -wofk  seems  to  us  to  be  the  best  Students'  Man- 
ual  we  have  seen"  —  Medico-Chirurgical  Revibw. 


JUST   PUBLISHED: 

A  New  Manual  of  Physiology. 

A  Course  of  Lectures  on   Physiology, 

As  delivered  by  Professor  KUss  at  tlie  Medical  School  of  the  University  of 
Strasbourg.  Edited  by  Mathias  Duval,  M.D.,  formerly  Demonstrator 
of  Anatomy  at  the  Medical  School  of  Strasbourg.  Translated  from  the 
Second  and  Revised  Edition,  by  Robert  Amory,  M.D.,  formerly  Pro- 
fessor of  Physiology  at  the  Medical  School  of  Maine.  150  Woodcuts 
inserted  in  the  text,     i  vol.  lamo.     547  pp.     Price  Jg2.5o. 

"M.  Kiiss  was  one  of  those  modest  scientists  who  love  science  for  itself;  who 
seek  for  the  truth  without  caring  whether  they  are  well  spoken  of  by  the  world."  — 
Gazette  H ebdo^nadaire, 

"  The  author  exhibits  a  thorough  familiarity  with  the  late  advances  made  in 
physiological  science  ;  and,  although  we  have  a  number  of  acceptable  works  on  this 
subject,  we  welcome  this  as  one  particularly  well  adapted  to  advanced  students.  Its 
terseness  gives  the  reader  and  student  an  impression  that  it  is  really  a  great  and  large 
work,  boiled  down  to  the  dimensions  of  a  handbook."  —  Cincinnati  Lancet  and 
Observer. 

"I  have  a  good  many  works  on  the  subject,  but  all  of  them  seem  to  me  in  some 
resoects  a  little  antiquated  ;  and,  in  the  examination  I  have  made  of  these  lectures, 
they  seem  to  me  to  meet  just  the  want  which  I  and  others  of  my  time  feel  very  ur- 
gently. I  am  also  pleased  to  have  some  new  illustrations,  after  meeting  the  old  stereo- 
typed ones  so  many  times."  —  Professor  Oliver  Wendell  Holmes. 

"  The  arrangement  of  this  manual  of  Physiology  is  judicious,  and  its  discussions 
of  the  various  subjects  involved  concise  and  accurate."  — Philadelphia  Medical  and 
Surgical  Reporter. 

°'  After  a  careful  reading  of  the  book,  we  do  not  hesitate  to  call  it,  on  the  whole, 
the  best  treatise  on  Physiologj',  of  its  size,  now  to  be  found  in  English.  Kiiss's  style 
is  full  of  vivacity  and  elegance,  and  abounds  in  picturesque  epithets  and  bits  of  de- 
scription, which  serve  both  to  fix  the  reader's  attention  and  to  impress  his  memory."  — 
Boston  Medical  and  Surgical  Journal- 

"  This  manual  is  the  only  concise  treatise  wherein  the  relations  of  Physiology  to 
Histology  are  carefully  presented,  in  the  English  language.  The  illustrations  are  both 
numerous  and  well  executed."  —  Physician  and  Pharmacist. 


For  sale  by  all  Booksellers,  or  forwarded  by  mail  to  any  part  of  the 
United  States  on  receipt  of  the  price  and  twenty -five  cents  extra^  to  prepay 
postage^  by 

JAMES    CAMPBELL, 

PUBLISHER,    BOOKSELLER,    AND    STATIONER, 

18  Tremont  Street,  Boston,  Mass. 


One  %olume.     i2mo.     Cloth.     $1.50. 

OF   THE 

Bromide  of  Potassium^  Bromide  of  Ammonium, 

Bromide  of  Sodium.^  and  Bromide 

of  Lithium, 

By  EDWARD    H.   CLARKE,   M.D., 

Professor   of    Materia    Medica    in    Harvard    University; 
AND 

ROBERT    AMORY,    M.D., 

Annual  Lecturer  for  1870-71  on  the  Physiological  Action  of  Drugs  on  Man  and 
Animals  in  the  Medical  Department  of  Harvard  University. 

The  work  consists  of  two  monographs,  supplementary  to  each  other:  Part  I.  treat- 
ing of  the  "  1  herapeutical  Action  of  the  Bromide  of  Potassium  and  its  Kindred  Salts," 
while  Part  II.  has  the  "Physiological  Action  of  Bromides  of  Potassium  and  Ammo- 
nium "  for  its  subject. 

NOTICES     OF     THE      PRESS. 
[From  the  Doctor,  London^  June,  1872.] 
"  Although  much  has  been  written  on  the  subject,  Drs.  Clarke  and  Amory  have 
succeeded  in  adding  a  really  valuable  little  volume  to  practical  Therapeutics." 

[From  the  St.  Louis  Medical  and  Surgical  Jourtial,  August,  1872.] 
"  We  regard  it  as  a  very  valuable  contribution  to  medical  science,  based  on  careful 
experiments  and  clinical  observation.     Every  practitioner  should  read  it." 

[From,  the  American  Journal  of  Insanity,  July,  1872.] 
"  We  commend  the  work  to  those  engaged  in  treating  diseases  of  the  nervous  sys- 
tem, and  to  the  profession  generally." 

[From  the  Richmond  and  Louisville  Medical  Joiirnal,  June,  1872.] 
"This  little  work  can  be  fully  recommended:  it  costs  little ;  it  is  concise,  lucid, 
physiologically  and  therapeutically  instructive;  embodies  much  ii  not  all  of  the  val- 
uable material  scattered  over  the  vast  field  of  Journalism ;  it  is  pleasantly  written, 
well  printed,  and  well  bound." 

[From  the  American  Journal  0/ Pharmacy,  June,  1872.] 
"The  medical  literature  in  both  essays  has  been  extensively  consulted,  criticall] 
examined,  and  carefully  compared  with  the  experiments  and  observations  of  i\i 
authors ;  thus  many  interesting  facts  have  been  established  which  must  prove  vei5 
valuable  to  the  medical  practitioner." 

[From  the  Philadelphia  Medical  Times  for  June,  1872.] 
"Given  a  pure  drug,  the  physidogist  experiments  with  it  upon  man  and  animals, 
carefully  noting  its  absorption,  its  elimination,  its  action  while  in  the  economy,  and 
deducts  certain  conclusions,  which  he  places  in  the  hands  of  the  therapeutist,  who,  not 
forgetting  the  changes  produced  by  a  pathological  condition,  is  guided  by  them  in  the 
treatment  of  disease.  Judging  by  this  standard,  we  pronounce  the  book  before  us  to 
be  a  model.  We  thank  Drs.  Clarke  and  Amory  for  their  contribution,  and  express  a 
hope  that  the  supply  of  such  books  may,  like  Tennyson's  brook,  '  go  on  for  ever.'  *' 

For  Sale  by  all  Booksellers. 

JAMES   CAMPBELL,   Publisher, 

Boston,  Mass. 


''  A  very  Judicious  treatment  of  a  very  delicate  sub- 
ject" —  Providence  Evening  Press. 


THE    PASSIONS 

3fn  tlietr  Kclation  to  |)ealtl)  anti  T>'m^^t, 

Translated  from  the  French  of  Dr.  X.  Bourgeois,  by  Howard 
F.  Damon,  A.M.,  M.D.     i  vol.  i2mo.    Cloth.    J1.25. 


The  following  are  a  few  of  the  notices  which  have  been  received :  — 

"  There  is  a  world  of  suggestions  for  the  management  of  the  passions  in  this  book, 
and  their  perusal  will  not  fail  to  work  personal  profit."  —  Massachusetts  Ploughman. 

"There  is  a  delicacy,  frankness,  candor,  and  evident  sincerity  about  the  composi- 
tion, that  convinces  even  the  casual  reader  that  the  author  and  translator  have  only 
the  welfare  of  their  fellow-men  at  heart.  It  is  a  treatise  on  Love  and  Libertinism, 
m  a  right,  proper,  and  intelligent  spirit,  and  of  incalculable  benefit  to  the  whole  com- 
munity." —  Thi  Common-wealth. 

"The  book  bears  no  trace  of  the  morbid,  unhealthy  spirit  characteristic  of  many 
French  books  upon  this  subject."  —  Boston  yournal. 

"  It  treats  in  an  exhaustive  manner  of  the  sensual  vices  common  to  human  nature, 
and  points  out  the  shoals  and  quicksands  upon  which  so  many  careers  are  wrecked 
through  perverted  indulgence  in  Love  and  Libertinism."  —  Saturday  Evening  Go- 
xette. 

"  A  careful  examination  of  the  book  will  satisfy  the  reflecting  reader  that  the  author 
treats  this  most  serious  and  difficult  topic  with  great  professional  ability,  and  with  a 
clearness  and  propriety  of  diction  and  a  cogency  of  argument  that  cannot  fail  to  be 
productive  of  much  good."  —  Boston  Daily  Globe. 

"  The  subject  treated  of  in  this  volume  is  of  importance,  because  of  the  general 
ignorance  among  all  classes  in  regard  to  it,  from  a  morbid  fear  of  enlightening  youth 
upon  the  physical  ills  engendered  by  misguided  passions."  —  Evening  Standard^ 
New  Bedford,  Mass. 

"  A  very  judicious  treatment  of  a  very  delicate  topic.  It  is  full  of  information, 
deals  practically  with  physical  and  social  sins,  shows  their  results  upon  the  system,  and 
is  a  powerful  medical  plea  for  virtue  and  social  morality." — Providence  Evening  Press. 

"  Many  parents,  married  people,  and  all  charged  with  watch  and  care  of  the  young, 
at  least,  might  derive  benefit  from  its  perusal." —  Congregatiofialist. 

"This  is  a  timely  and  highly  meritorious  work." —  The  All  Day  City  Itemj  Phil- 
adelphia. 

'*  It  treats  a  delicate  subject  in  language  that  is  unobjectionable  to  the  most  fas- 
tidious, and  the  information  it  contains  cannot  fail  to  do  a  vast  amount  of  good  in  the 
age  of  loose  morals.  The  debasing  and  unnatural  habits  of  modern  society  and  their 
fearful  consequences  on  the  race  are  depicted  in  a  startling  manner.  Immorality  and 
its  inevitable  train  of  diseases  are  warned  against."  —  Sandy  Hill  Her aldy  N.Y. 


Published  by  JAMES   CAMPBELL, 

Boston.^  Afass, 


THE 

Gynecological  Record.- 

A    BOOK   OF   BLANK    FORMS, 

Intended  as  an  aid  to  the  busy  practitioner  in  recording  G_ynse- 
cological  Cases;  with  an  Appendix  of  Blank  Leaves,  and  Tables 
for  the  ready  analysis  of  the  contents  of  the  book.  Prepared  by 
Joseph  G.  Pinkham,  A.M.,  M.D.,  &c.  Approved  by  the  Gynae- 
cological Society.  One  volume,  quarto,  half  bound  in  leather. 
Price,  $2.50.    Postage,  50  cents  extra. 


EXTRACT    FROM    THE    PREFACE. 

"  This  book  is  intended  to  aid  the  busy  practitioner  in 
making  detailed  and  systematic  records  of  cases  occurring  in 
his  Gynaecological  practice.  Its  scope  will  be  obvious  on  inspec- 
tion. Blank  forms  are  furnished  which  can  be  filled  out  with 
comparatively  little  labor.  As  the  same  method  and  order  of 
examination  is  preserved  in  each  case,  a  proper  basis  for  com- 
parison is  secured;  and  the  minuteness  of  detail  required  to  fill 
out  the  forms  renders  the  physician  less  liable  to  overlook 
points  of  interest.  Under  the  head  of  "History"  is  supposed 
to  be  given  the  patient's  own  account  of  her  clinical  life  previous 
to  date,  so  far  as  otherwise  not  brought  out.  The  diagrams  will 
serve  the  purpose  of  illustrating  the  case.  On  the  one  repre- 
senting the  anterior  aspect  of  the  body  may  be  given  the  outline 
of  any  tumor,  area  of  tenderness,  &c. ;  on  the  other,  the  relative 
position  of  the  several  pelvic  organs,  as  seen  on  a  median  sec- 
tion. The  tables  for  the  analysis  of  cases  are  few  in  number 
and  simple  in  their  plan." 

'*  The  forms  are  very  carefully  brought  out,  and  will  be  of  great  advantage.  They 
will  serve  not  only  as  a  record,  but  as  a  complete  reminder  of  what  to  observe  in 
these  cases,  and  will  add  much  to  the  accuracy  of  the  diagnosis,  and  consequently  to  the 
success  of  the  treatment."  —  Medical  and  Surgical  Reporter,  Dec.  24,  1870. 

"  It  seems  to  us  to  fill  most  of  the  requirements,  and  we  cordially  recommend  it." 
—  New  York  Medical  Journal,  Jan.  1871. 

"  The  book  is  neat,  and  neatly  gotten  up."  — Lancet  and  Observer. 

"  If  these  cases  be  well  selected  and  carefully  kept,  even  should  only  one  book  be 
filled  by  each  practitioner,  it  would  make  a  contribution  to  Gynaecology  which,  before 
many  years,  would  enable  us  to  settle  definitely  many  points  in  the  natural  history  and 
therapeutics  of  utenne  diseases  which  a.e  ucwmost  obscure  and  unsettled."  —  Medicai 
Times. 

"We  note  with  pleasure  the  use  of  diagrams  with  each  blank,  representing  in 
outline  the  anterior  aspect  of  the  abdomen,  and  a  section  of  the  pelvis."  —  Boston 
Mtdicai  and  Surgical  Journal. 

JAMES   CAMPBELL,   Publisher, 

Boston^  Mast- 


1   Vol.     16ino,  cloth.     41  Illustrations.     $1.75. 
THE 

HANDBOOK  FOR  MIDWIVES, 

BY 

Henry  Fly  Smith,  B.  A.,  M.  D.,  Oxon. 
-il     111  u»t:i*£it  ions. 


I 


The  midwife  will  find  in  the  following  pages,  described  in  familiar 
language,  all  the  information  necessary  for  a  thorough  understanding 
of  so  much  of  the  art  of  midwifery  as  belongs  to  her.  Technical 
words  and  phrases  are  added  and  explained,  so  that  she  may  be  able 
to  understand  the  orders  and  remarks  of  the  accoucheur,  when  his 
scientific  assistance  is  required. 

A  general  anatomical  sketch  of  the  human  body  is  given,  with  an 
exact  description  of  the  parts  concerned  in  the  business  of  conception, 
pregnancy  and  delivery.  The  progress  of  pregnancy  and  its  signs, 
the  management  of  natural  labor,  and  of  the  lying-in  state,  are 
minutely  detailed.  The  diseases  and  accidents  peculiar  to  each  con- 
dition, the  signs  and  symptoms  of  wnnatural  labor,  and  the  treatment, 
are  fully  described  as  far  as  the  midwife  requires  for  her  guidance, 
and  for  the  recognition  of  impending  danger,  demanding  the  atten- 
tion of  the  accoucheur. 

Drawings  and  diagi-ams  are  introduced  wherever  they  can  be  of 
service  in  facilitating  the  understanding  of  the  text.  The  scope  of  the 
book  has  been  generally  regulated  by  the  German  manual  for  mid- 
wives,  writen  by  Dr.  B,  Schultze,  Professor  of  Obstetrics  in  the  Uni- 
versity of  Jena.  The  works  of  Cazeau,  Churchill,  Ramsbotham, 
Pwayne,  Meigs,  Bedford  and  other  authors  have  been  consulted 
throughout,  and  due  acknowledgment  is  here  ofifered  for  the  use 
made  of  their  well-known  standard  writings. 

JAMES  CAMPBELL.  Publisher.  Boston.  Mass. 


A  NEW  BOOK  ON  SANITARY  SCIENCE. 


FILTH      DI  SEASES 

AND    THEIR    PREVENTION, 
By  JOHN  SIMON,  M.D.,  F.R.C.S., 

CHIBF  MBDICAL  OFFICER  OF   THE    PRIVY  COUNOL  AND  OF  THE   LOCAL   GOVERNMENT 
BOARD   OF   GREAT   BRITAIN. 

FIRST    AMERICAN    EDITION. 

Printed  under  the  direction  of  the  State  Board  of  Health 
of  Massachusetts.     i6mo.     Cloth.     $i.oo. 


The  undersigned  members  of  the  Massachusetts  State  Board 
of  Health  would  respectfully,  but  earnestly,  urge  upon  all  per- 
sons the  careful  perusal  of  the  following  masterly  essay  by 
Mr.  Simon,  Chief  Medical  Officer  of  the  Privy  Council  and  of 
the  Local  Government  Board  of  England.  If  the  practical  sug- 
gestions made  therein  were  acted  on  by  all  citizens,  hundreds 
of  lives  now  annually  doomed  to  destruction  would  be  saved, 
and  the  health  and  comfort  of  the  people  greatly  increased. 

Henry  I.  Bowditch, 

Richard  Frothingham, 

j.  c.  hoadley, 

R.  T.  Davis, 

Daniel  L.  Webster, 

J.  B.  Newhall, 

W.  L.  Richardson,  Sec'ypro  tern., 

Members  of  the  State  Board  of  Health  of  Massachusetts. 


PUBLISHED   BY 

JAMES    CAMPBELL,    BOOKSELLER, 

JSoston,  Mass. 


DATE   DUE  SLIF* 

UNIVERSITY  OF  CAIilFORNIA  MEDICAL  SCHOOL  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


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